DIY Off-grid Solar System Guide

Author

Brad Brown

About the Author

Brad Brown is a Silicon valley computer programmer that lives in California.

Last Updated

8/26/2025

Status

This document is currently in development and still being updated until further notice here.

Disclaimer

General

Although, I try to make this document accurate, I'm not responsible or liable for any errors. I'm not responsible or liable for any problems or damages that you might encounter with your solar system if you use any information from this document. In addition, any work you do with solar system is done at your own risk.

Warning High Voltage

You can encounter high voltages from solar systems, including solar panels, charge controllers, batteries, and inverters, that can be dangerous and deadly so always take proper safely precautions when handling high voltages. This document is not intended to teach you how to work with high voltages. In addition, any work you do with high voltages is done at your own risk.

Overview

The DIY Off-grid Solar System Guide shows how to create a DIY off-grid solar system for use in the United States paying particular attention to saving money.

I live in California with the highest electricity rates in the nation so to save money I need to get a solar system. In 2024, my rates in California are about 47 cents a KWH compared to Las Vegas rates of about 12 cents a KWH; therefore my rates are about 4 times more than Las Vegas. To put that into perspective, if I run a 1000 watt space heater for 2 hours it will cost me almost $1 and it would cost someone in Las Vegas about $0.24 cents.

I want to make sure when I buy a solar system that I'm buying what I need so I don't waste my money.

I'm going to focus on the lowest cost solar systems under $1000, that are capable of running most 120V home appliances. I'm not going to focus on large whole house solar systems but you can use the information here to build as powerful of a solar system as you want.

I'm going to use this document when I build my solar system and I'm providing it free to others to help them build their solar systems.

The requirements for my solar system are:

Off-grid: With an off-grid solar system you generally won't need permission from the government or any permits.
Saves Money: I would like a payoff period of three years or less.
Expandable: I don't want to spend a lot of money all at once so when possible I want a system that is upgradable.

This guide won't cover how to do the following topics but I will mention them so you know they exists.

Grid-tied solar system.
Government subsidies.

Off-grid vs Grid-tied

A solar system can be either off-grid or grid-tied.

Off-grid solar system

Inexpensive solar system cost: Typically installed as a DIY project but you could hire a professional to install it for you if you want. The solar system could cost as little as about $500 for a very small system.
Inexpensive maintenance and repair cost: If you installed the solar system yourself then you can do maintenance and repairs yourself to save money.
No net metering: Can't sell electricity back to the grid.
No Permit Required: In general, you don't need a permit for an off-grid solar system but you might need a permit in some cases depending on what you want to do and where you live. For example, if you want to install a transfer switch to your breaker box a permit might be required in some cities but installing a transfer switch is optional.
No Power Outages: Often a grid-tied solar system can't provide power during a power outage due to regulations that require shutting off power for safely reasons to protect line workers. However, an off-grid system can supply electricity when there is a grid power outage.
Portable: An off-grid solar system doesn't have to be permanently attached to a structure and can be used in an apartment.
No Government Involvement: No fees. no taxes, no regulations, and no inspections. Permits are not required for most things, but depending on what you want to do a permit might be required.
UL Listed Not Required: In the United States, for a grid-tied system, you probably need UL listed products but for off-grid you don't but it is always nice to have.
Not easy to use: When not connected to your houses existing electrical system it is not going to be as easy to use as a grid-tied system because you have to do extra work to distribute the electricity around your house. It is possible to install a transfer system to connect it into your houses electrical system and in that case could be easier to use but even then is not likely as easy to use as a grid-tied solar system.

Grid-tied solar system

Expensive solar system cost: Typically installed by professionals and cost $10,000 and up depending on how much power you want.
Expensive maintenance and repair cost: You typically can't do maintenance and repairs yourself.
Net metering: Net metering means selling solar electricity back to the grid. If you are grid-tied some power companies allow net metering. The amount you get from net metering varies with each power company.
Permit Required: Typically a permit is required to connect a grid-tied solar system to the houses grid electricity. However, there are DIY grid-tied solar systems that might or might not be legal and might or might not require a permit.
Power Outages: Often a grid-tied solar system can't provide power during a power outage due to regulations that require shutting off power for safely reasons to protect line workers.
Not portable: A grid-tied system has to be connected to your grid electricity on a house so generally can't be portable.
Government Involvement: Government involvement might include fees, taxes, regulations, inspections, and permits.
UL Listed Required: In the United States, for a grid-tied system, you probably need UL listed products but for off-grid you don't but it is still nice to have.
Easy to use: When the solar system is grid-tied to your houses electrical system it is generally easy to use and you use your electricity just like your always have.

Reference: https://www.youtube.com/watch?v=W2mylQf8jec

What does off-grid mean?

Off-grid means your solar system is not connected to the grid but it does not mean your house is off-grid. In fact, in most cities it is not even legal to have your house off-grid so in most situations your house will have to be on-grid.

Even though your house is on-grid you don't have to use any grid electricity; however, most cities require paying a monthly minimum grid-connection fee even if you don't use any electricity.

Since in most cases you have no choice but being connected to the grid and paying a minimum fee you might as well just consider the grid as backup power for your solar system. Even if you don't want to pay for a grid connection it is good to have unlimited backup power available just in case you need it.

Government Solar Subsidies

As of 2024. Both a professional installed grid-tied solar system and a DIY off-grid solar system can qualify for government solar subsidies such as the Federal Solar Tax Credit. As of 2025, the Federal Solar subsidies might be discontinued but you can check if state or other local subsidies are available in your area.

However, most if not all of the government solar subsidies available are tax credits, not cash payments so not everyone qualifies. You might not earn enough to get the subsidy, or you might earn too much to get the subsidy.

Note that sometimes you might see advertisements for free solar from the government for low income but as far as I know there is no such thing as free solar.

I'm not going to cover government solar subsidies, but you could ask a CPA or tax professional if you are interested in getting them.

When I create my DIY solar system I'm not even going to try to get any government solar subsidies, so I will pay the full cost of my solar system out of my own pocket. The reason is because I don't want to bother with the complexity of tax forms to try to figure out if I can get the tax subsidy from the government. However, for those that want to do the extra work you might be able to save extra if you qualify for a tax subsidy.

Cash vs Debt vs Lease Purchase

Lease is a type of rental agreement where you don't own the solar panels placed on your house. I would not even consider using a lease to get solar.

If you get a loan to buy solar it will cost more because of the interest you have to pay so I would not use a loan myself.

In addition, if you get lease or to get solar and want to sell your house in the future it can reduce the value of your house because not everyone will want to pay or be able to pay for your solar lease or loan.

When I buy a solar system I will pay cash to save money.

Ground vs Roof Installation

I would not want to install solar panels on the roof.

Solar panel maintenance: It is safer and easier to clean, repair, and maintain your solar panels if they are installed on the ground.
Roof repair: If a roof needs to be replaced or repaired it might cost more if solar panels are on the roof.
Homeowners insurance: If you install solar panels on your roof your homeowners insurance company might drop you. Check with your homeowners insurance company before installing solar on your roof and find out if they allow solar panels on your roof or if your rates will go up.

How to Connect Solar Electricity to House

There are several ways you can connect electricity from your solar system to your house.

Off-grid using extension cords. This is the easiest way to use solar in an apartment.
Off-grid using a transfer switch to breaker box. How I Cut My Electric Bill Using a Transfer Switch and Power Station!
Off-grid using an interlock kit to breaker box.
Grid-tie to outlets: This requires a grid-tie inverter that plugs into an outlet. See inverter section for more info.
Grid-tie direct to breaker box: This requires government and power company approved equipment to connect to the breaker box and requires a permit. This method is generally not a DIY project; although, it is possible and legal to DIY on your own house in some states but you will still need a permit. It probably is not legal to DIY on someone else's house unless you are a licensed electrician. Method five will not be covered by this document.

Electricity Rates by State

California has the highest electricity rates in the country at an average of $0.29 per KWh and Washington has the lowest at an average of $0.11 per KWh. Keep in mind these are the average rates in the state so the rate in different cities can be higher or lower.

Reference: https://www.chooseenergy.com/electricity-rates-by-state/

Electricity Rates California

Highest Rates

California has the highest electricity rates in the United States.

In the past there was only one rate for electricity; however, today rate there are many different rate plans similar to cell phone company's that have many rate plans.

As of 2023, in California, I'm on the PG&E tiered plan and I pay a minimum of $0.47 per KWh so my rate is higher than the average rate in California of $0.29. My $0.47 rate increases on higher tiers. There are currently 3 tiers; although, they don't call the last tier a tier so they say there are 2 tiers. They are also increasing rates for 2024 and likely every year after that so my rate is expected to only go up higher.

Some cities such as Las Vegas in other states have rates about $0.12 per KWh so I am paying about 5 times more than the lowest price rates in other states.

California government policy

In the past electricity generation was centralized and produced by power companies. Now the government wants electricity decentralized and produced by the individual using solar panels.

In my optional, the reason electricity rates in California are higher than other states is government policy. The California policy is to price grid electricity rates high making it too expensive to use for many so those that can't afford it are forced to either go without or buy solar panels to save money.

California has the highest housing prices in the nation which means fewer people can buy a house so they are forced to rent. Renters can't easily install solar panels so they are forced to pay the high price of electricity.

High electricity rates will hurt poor people but won't have any effect on rich people because they won't have any problem paying the higher prices or buying solar panels to save money.

Reference: Why California Electricity Is So Expensive | Susan Shelley

Grid Connection Fee

High electricity rates encourages people to stop using electricity from the grid which would eventually put power companies out of business.

Unfortunately, the law in most cities requires being connected to the grid and paying a Grid Connection Fee each month whether you use any electricity or not.

As of 2024, California’s PG&E’s minimum fee is $11.90 per month according to the company’s website.

On 5/9/2024, the Public Utility Commission (PUC) passed a new income based flat fee plan that will replace this old $11.90 per month grid connection minimum fee.

Reference: https://www.pge.com/en_US/residential/rate-plans/how-rates-work/rate-changes/minimum-bill-charges/minimum-bill-charges.page

Income Based Fixed Rate Electricity Plan

On 5/9/2024, the Public Utility Commission (PUC) in California passed an income based flat fee of about $24.99 per month with possible discounts if you can prove you are low income. There will be a small decrease in the rate per KWH but they will just raise it in the future so it won't really help.

In addition, I assume it will be difficult to apply and get the low income discount so most people will never bother.

It is important to note that this is not really a flat fee, it is a flat fee plus the rate per KWH. This means that even if you use zero electricity you have to still pay the flat fee. PG&E actually had a fixed flat fee for everyone before this new plan that was $11.90 a month even if you use zero electricity.

This plan is supposedly to help the poor; however, I think the real reason for this income based pricing scheme is that many solar users are essentially zeroing out their electric bills and the power companies want to increase the minimum fees so that those using no electricity with solar will have to pay a higher minimum fee for being connected to the grid.

"Flat Fee" Utility Scam!

Is Solar Worth it?

I live in California with the highest electricity rates in the country, so if solar is worth it anywhere, it will be worth it here.

I have PG&E and in 2024 my was about 0.50 per kWh compared to Las Vegas rates of about 0.12 per kWh so my cost is about 5 times more than Las Vegas.

While trying to conserve electricity I pay about $100 a month in electricity or $1200 a year; however, if I wasn't trying to conserve I might use twice as much electricity as I'm using now.

If I didn't try to conserve electricity it would increase my qualify of life. For example, to conserve electricity right now I don't use the heat dry mode on the dishwasher which means I have to dry my dishes outside of the dish washer taking extra time and effort and reducing my qualify of life.

Below are things I do to try and save gas or electricity.

Don't use the central gas heater or electric space heater.
Don't use heat dry on dishwasher.

Thing that I use electricity on.

Clothes dryer.
Refrigerator.
Dishwasher.
Toaster.
Microwave.
Electric garage door opener.
Vacuum cleaner.
Computer.
Phone.
TV.
House lights.
Electric toothbrush.

The amount I save depends on how much electricity I would use if not conserving electricity, not how much I am actually using now while conserving electricity.

If you wanted to keep track of exactly how much you actually save you would need to keep track of how many kWh of solar electricity you use and most people don't keep track of that.

The main factors to determine if solar is worth it are:

Electricity rates.
How much electricity you use.
Cost of your solar system.

In California with high rates, I think solar can be worth it, but in places like Las Vegas with low rates it would be much harder to make it worth it.

In California it is current government policy to make electricity rates as high as possible so this will force many to consider solar or go without electricity. It is clear that the government does not want to do anything that would lower electricity rates. Unless the government policy changes, electricity is only going to get more expensive as time goes by. The only way I can save money on electricity is either conserve or get solar.

Solar Tariffs

Often solar systems in other counties will be significantly cheaper than in the United States because of tariffs.

The tariffs are determined by the government and can change anytime. However, once a tariff is put in place they tend to not want to remove them because the government likes taxes. For example, Trump put tariffs on China and Biden kept them and even increased some of them.

Tariffs could be any amount, even over 100%.

Tariffs are a hidden tax because they don't show the tax on the sales receipt like sales tax.

Tariffs are going to increase the price you pay. The bottom line is tariffs are going to increase the cost of solar regardless if the part is manufactured in China or the USA because domestic manufacturers will increase their prices because of less competition from China.

The government has had a solar tax credit that you can get on your taxes if you qualify and apply for it but they also add tariffs to make solar more expensive. Basically the government makes it look like they are helping you when in reality they are making things more expensive for you and not helping you at all.

Why SOLAR Panels Cost 3X MORE in USA vs Europe - The Hidden Truth About Solar Pricing 2025

kWh used by appliances

The section shows the energy used by common household appliances so you can see how you might save money. So for example, a mini refrigerator uses less electricity than a top refrigerator so switching to a mini refrigerator would save you money if powering the refrigerator from the grid.

Top Refrigerator: Mora 18 cu. ft. Top Freezer Refrigerator ($579.99 price as of 7/5/24) 403 kWh per year
Mini Refrigerator: Danby 3.3 cu ft Compact All Refrigerator ($229.99 price as of 8/21/24) 259 kWh per year
Chest Freezer: Hisense Garage Ready 17.7 cu. ft. Convertible Chest Freezer/Refrigerator ($599.99 price as of 7/5/24) 334 kWh per year
Coffee Maker = 9 kwh per month
Dishwasher = 30 kwh per month
Hot Plate = 4 kwh per month
Microwave Oven= 16 kwh per month
Range with Oven= 58 kwh per month
Slow Cooker= 12 kwh per month
Toaster= 3 kwh per month
Waffle Iron= 2 kwh per month
Blender, Can Opener & Food Mixer= less than 1 kwh per month
Dryer= 75 kwh per month
Iron= 5 kwh per month
Washing Machine= 9 kwh per month
Vacuum Cleaner= 4 kwh per month
Hair Dryer= 2 kwh per month
Heating Pad= 1 kwh per month
Curling Iron, Shaver = 1/2 kwh per month
Radio = 7 kwh per month
LCD Television = 27 kwh per month

Cost to run appliances from grid

Use the formulas below to determine the cost to run various appliances when using electricity from the grid.

Calculate Wh: [Watts of device] × [Total hours appliance used] (Example: 7500 Wh = 750 W × 10 hours)
Convert Wh to kWh: kWh = Wh ÷ 1,000
Calculate total cost: kWh × [Your kWh rate].

Examples

In the examples below I am using my cost of electricity in California of $0.47 per kWh.

60 Watt incandescent light bulb for 1 hour ($0.0282)

Note that this example is using an old fashion 60 watt incandescent light bulb, not a new LED 60 watt equivalent light bulb which would use much less power.

60 Watts * 1 hour use = 60 Wh
60 Wh / 1000 = 0.06 kWh
0.06 kWh* $0.47 kWh rate = $0.0282

1000 Watt space heater for 1 hour ($0.47)

1000 Watts * 1 hour use = 1000 Wh
1000 Wh / 1000 = 1.0 kWh
1.0 kWh* $0.47 kWh rate = $0.47

Payback time

Here are reasons someone might want solar.

To save money.
As a backup to the grid electricity going down.
You can't use grid electricity because you live outside of the city or in an RV.
You don't want to use grid electricity to save the environment..

If your reason is anything other than, number one, to save money then the cost might not be your primary concern. As an example, if you want solar for a backup if the grid goes down you might not care if you save money.

To save money, the cost of the solar system must be paid back in savings from your electricity bill. Everything after you paid back the cost of your solar system will be profit.

If you want solar to save money, you don't just want to save money, you want to save money in your lifetime so that is why a fast payback time is important. The faster the payback the more money you will save.

For those that want to save money I think a payback period of several years or less should be the goal for any solar system.

Here are factors that effect the payback time.

Cost of the solar system. Lower cost equals faster payback.
Government subsidies. Government subsidies equals faster payback. Government subsidies are not covered in this document.
How much electricity you want to use. The more electricity you use, the faster the payback.
Cost of electricity in your city. The higher the cost of electricity, the faster the payback.
Selling back electricity to the power company. Selling back electricity equals faster payback. Only relevant to grid-tied solar systems. Grid-tied solar systems are not covered in this document.

Note that most power companies have a minimum monthly fee that you have to pay even if you use zero electricity so in most situations you won't be able to have a zero power bill. If you live in an area that allows selling electricity back to the power company it might be possible to zero out your electric bill but that requires a grid-tied solar system which is not covered in this document.

Refrigerator Payback

The analysis of the payback period of running a refrigerator on solar is a good exercise to determine if solar will be worth it for you. In other words, if you can't get a good payback period from running your refrigerator on solar than you probably can't get a good payback period at all with a larger solar system.

To summarize the results below, at my electricity rate in California of about $0.50 per kWh, a standard refrigerator uses about $17 a month and a mini refrigerator uses about $11. The payback time on both for just the solar panels and batteries is around 2 to 3 years.

In my opinion, it would be worth it with my electricity rate in California but the payback period is still longer than I would like. I would prefer a 1 year or less payback. To get a lower payback time solar panels and batteries prices would need to drop more in price.

Standard Refrigerator Payback time

This is an estimate of payback time of the cost of the solar system to run the refrigerator not including the cost of the refrigerator.

In this estimate I am using the Mora 18 cu. ft. Top Freezer Refrigerator from Costco that cost $579.99. I am using the Energy Guide estimate of 403 KWh per year. I am using my cost of electricity in California of about 0.50 per KWh.

403 KWh per year x 0.50 California cost per KWh = $201.50 per year / 12 months = $16.79 per month.

In this estimate I am only taking into account how many solar panels and batteries are needed because they will be mostly fully utilized to run the refrigerator and are the most expensive components.

To run a standard refrigerator you will need about 400 watts of solar panels and a 12V 200 ah LifePo4 battery.

At the time of this writing a 100 watt solar panel is about $50 and a 12V 100 ah battery is $150; therefore, total cost for 4-100W solar panels and 1-100 ah batteries is $200 + $300 = $500.

The payback time is $500/ $16.79 = 30 months or 2.5 years.

Mini Refrigerator Payback time

This is an estimate of payback time of the cost of the solar system to run the refrigerator not including the cost of the refrigerator.

I am using the product below in this estimate.

Mini Refrigerator: Danby 3.3 cu ft Compact All Refrigerator $229.99, 259 kWh per year

I am using my cost of electricity in California of about 0.50 per KWh.

259 KWh per year x 0.50 California cost per KWh = $129.50 per year / 12 months = $10.79 per month.

In this estimate I am only taking into account how many solar panels and batteries are needed because they will be mostly fully utilized to run the refrigerator and are the most expensive components.

To run a mini refrigerator you will need about 200 watts of solar panels and a 12V 100 ah LifePo4 battery.

At the time of this writing a 100 watt solar panel is about $50 and a 12V 100 ah battery is $150; therefore, total cost for 2-100W solar panels and 1-100 ah batteries is $100+ $150= $250.

The payback time is $250/ $10.79 = 23 months or 1.9 years.

Low Energy Appliances

A lot of appliances were designed when energy was plentiful because the government provided cheap energy on the grid; however, it is expensive for you to provide off-grid solar energy.

In this section we look at if you should buy new low energy appliances as a replacement for high energy appliances to run off solar.

An example, a space heater was designed to be used with grid power. You can still use a space heater with solar but it can be very expensive especially when running on battery power. So an alternative appliance would be a heat pump that uses less power.

What loads are most practical to run on solar?

You can run any load on solar but some loads require so much power that it might not be practical economically.

Solar is best suited to running loads that are either low wattage (i.e. 7 watt LED lightbulb for 12 hours a day) for long periods of time or high wattage (i.e. 1000 watt toaster for 5 minutes) for short periods of time.

Running high wattage loads for long periods of time is generally not practical (i.e. 1500 watt space heater for 24 hours a day) because the solar system required would be so expensive that it is not cost effective.

Small Appliances: Small appliances such as a instant pot, toaster, toaster oven, coffee maker, blender, mixer, can all be run on solar for short periods of up to 10 minutes several times a day without a problem.
Microwave: A standard microwave could be run on solar; however, an inverter microwave is better because they use less power. A standard microwave uses full power in an on and off manner when set to a lower power setting. An inverter microwave when set to a lower power setting actually uses less power. A standard microwave that is rated at 1000 watts would use about 40% more power or about 1400 watts total. So although you can run a standard microwave it will require more power than an inverter microwave.
Heating: Heat pumps can heat or cool a house. Small heat pumps are best for solar and some can run on around 300 to 400 watts. It is generally not practical to run a resistive space heater on solar because of how much power they use.
Air Conditioning: An air conditioner can be run off of solar but they do require at least around 400 watts for a small window air conditioner. You can also run them off of batteries but that would require a lot of battery power so it generally is not a good idea.
Clothes Dryer: I would not try to run a 240V clothes dryer because of the added expense of a 240V solar system. I would buy a 120 volt electric clothes dryer that is resistive or uses a heat pump. A heat pump dryer would be the best because it uses less energy. I would estimate about 1500 watts for a 120V resistive heat clothes dryer and about 500 watts for a 120V heat pump clothes dryer.
Water Heater: You can use a 120 volt resistive water heater or 120 volt heat pump water heater.
Oven: A 220 Volt Oven requires too much power to be practical to run off of solar. There are 120 Volt heat pump ovens as an alternatives.
Stove Top: Use a 120V AC induction cook top.
Refrigerator: A standard refrigerator might use 6.8 amps or 816 watts but a mini refrigerator might only use 75 watts. In addition, a DC refrigerator won't require running an inverter all day so might save energy that way too.
220 Volt EV charger: I need to do more research on this subject so I will add more here later.

Low Energy Appliance Examples

COSTWAY Portable Washing Machine, Twin Tub 26lbs Capacity Laundry Washer, 18lbs Washer and 8lbs Spinner Combo with Timer Knobs, Built-in Drain Pump, Compact Washer for Home Dorm Apartment, Blue+White $159.99

Price per Watt vs Cost per kWh

There are two main ways to calculate the cost of a solar system:

Price per watt (PPW): Compares multiple solar system. Total system cost / Total Watts.
Cost per kilowatt-hour (cents/kWh): Compares the cost of solar versus grid energy. Total cost / Lifetime kWh produced.

Cost per kWh

The estimate for cost per kWh would be the entire cost of the system including maintenance cost for the life of the system divided by the kWh produced during the life of the system as shown below.

Total cost of solar system / Total kWh produced

Batteries are optional depending on if you want electricity at night and add to the cost of the solar system. If you have fewer batteries you will get a lower cost per kWh but you might not have enough electricity at night when you want it. In other words, batteries add to the total cost of the solar system and will increase your cost per kWh .

I'm using a lifespan of 30 years for the solar system.

100 Watt Solar System Cost per kWh

A 100-watt panel for an average of four hours of sunlight produces about 0.4 kWh per day.

1000W 12V Solar System Total $314.95 + Wiring = about $400.

0.4 kWh per day x 365 days in year = 146 kWh per year x 30 year lifespan = 4,380 kWh in lifespan.

$400 total cost / 4,380 kWh per lifespan = 0.10 per kWh .

200 Watt Solar System Cost per kWh

A 200-watt panel for an average of four hours of sunlight produces about 0.8 kWh per day.

1000W 12V Solar System Total $314.95 + Wiring + $100 extra solar panel = about $500.

0.8 kWh per day x 365 days in year = 293 kWh per year x 30 year lifespan = 8,760 kWh in lifespan.

$500 total cost / 8,760 kWh per lifespan = 0.05 per kWh .

Solar System

A solar system typically has four components consisting of a solar panel, charge controller, battery, and inverter.

However, components can be combined in one device. The disadvantage of combining components is it is less flexible and might cost more to repair.

One combination is a solar generator that combines a charge controller, battery, and inverter in one device so you only need to add a solar panel.

Another combination is called a hybrid system with the charge controller and inverter in one device that you can add solar panels and batteries to.

Solar Panels: Produces electricity from the sun. If you just want battery backup incase of power failure then you would not need solar panels.
Charge controller: A charge controller is a battery charger that uses electricity from solar panels to charge the battery. If you just want battery backup incase of power failure then you would not need a charge controller.
Battery: The battery stores power from generated from the solar panels for use when there is no sun. Both off-grid and grid-tied solar systems can be designed without a battery. Most off-grid systems use a battery; however, many grid-tied systems don't use a battery and rely on the grid when there is no sun.
Inverter: Converts power from your battery to 110 or 120V AC for use with household appliances. You only need an inverter if you want 120V AC power.

Solar Panels

What type of solar panel is best?

There are three basic types of solar panels, monocrystalline, polycrystalline, and thin film.

Polycrystalline is about 18% efficient compared to monocrystalline 22% efficient; however, polycrystalline is usually cheaper because it is easier to manufacture.

In my opinion, I would generally buy polycrystalline if it is cheaper than monocrystalline because there is not that big of a differences in performance between the two. However, monocrystalline seems to be more popular and therefore more available so you might have trouble finding a polycrystalline panels so that might be a reason to pay more for monocrystalline if that is all you can find offered in the size you want.

Thin-film are flexible, not as rugged, and generally cost more so they are usually best for portable solar panels or for mounting on cars.

Types of solar panels: which one is the best choice?

Amazon Solar Panel Tests! (HQST Mono vs Poly)

What is a shade tolerant solar panel

Another type of solar panel is the shade tolerant solar panel available in either rigid or flexible form. It is designed to provide more power when some cells are shaded; however, these panels are usually more expensive. If your panels are never in the shade you don't need this feature.

What is the difference between mono-facial & bifacial solar panels

Mono-facial solar panels only work on one side.

bifacial solar panels work on both sides and are supposed to be more efficient because it can generate electricity from both sides of the panel. From the backside the panel can only get reflected light so it can't produce as much from the back as it can from the front. Bifacial panels cost more but might create more electricity from the same area compared to Mono-facial. However, generally you have to mount the bifacial solar panels higher so light can get underneath so more often they are mounted on the ground rather than a roof.

You will have to decide if the extra cost of bifacial solar panels is worth any extra power you get in your application.

How many kWh does my solar panel produce per day?

The KWh produced by a solar panel = Solar Panel Watts x average hours of sunlight per day.

A 100-watt solar panel over an hour will produce 0.1 kWh. For an average of four hours of sunlight a day it produces 0.4 kWh per day.

How many watts of solar panels do you need to charge your battery?

Using the online calculator below you need 260W to charge a 12V 100 Ah battery in 6 hours.

https://footprinthero.com/what-size-solar-panel-to-charge-100ah-battery

Battery Voltage (V): 12
Battery Amp Hours (Ah): 100
Battery Type: LifePO4
Battery Depth of Discharge (DoD): 100%
Solar Charge Controller Type: MPPT
Desired Charge Time (in peak sun hours): 6
Estimated solar panel size: 260 watts

How long to charge my battery?

To find out how long it will take to charge your battery you must calculate Sun Hours per day using an online calculator for your ZIP code.

https://smartgreensolar.com/sun-hours-calculator/

The online calculator should give you your Average Annual Sun Hours per day. An example, would be 4.6 Sun Hours per day.

A 100 Watt solar panel X 4.6 Sun Hours per day = 460 Wh.

A 1280 Wh battery / 460 Wh = 2.78 days to fully charge.

How many amps does a 100 watt panel produce?

Calculate the current in amps by dividing power in watts by the voltage in volts. When a 12V solar panel is rated at 100W, that is an instantaneous voltage rating. So if all of the test conditions are met, when you measure the output, the voltage will be about 18 volts. Since watts equals volts times amps, amperage will be equal to 5.5 amps (100 watts divided by 18 volts) . So your panel will produce 5.5 amps per hour.

Example: A 12 volt 100 watt solar panel will produce about 5.5 amps at 18 volts.

Adding solar panels in series or parallel

You can add one or more solar panels by connecting them in series or parallel.

Series: Add the voltage and take the lowest amps. Lower amps allow using thinner wire to connect panels to the charge controller.
Parallel: Add the amps and take the lowest voltage. This allows keeping the voltage lower so you don't go over the voltage max input for your charge controller.

Generally, it is better to have solar panels that match the voltage and amps but that is not required.

As an example, if you have two 12V solar panels connected in series but one is 10A and the other is 5A than the output will be 5A so you will lose 5A of potential output power because they are mismatched.

Should I connect my solar panels in series or parallel?

Choosing to connect solar panels in series or parallel often depends on the type charge controller you are using. With PWM, parallel is often required or else the voltage would be too high. With MPPT, series is often better because the higher voltage keeps the amps low allowing you to use thinner wire.

You can also use a combination where some panels are in series and some parallel.

What gauge wire should I use to connect the solar panel to the charge controller?

10AWG is a typical value to use for most applications.

Why does a 12V solar panel have a voltage of around 17V?

A solar panel that is called 12V produces around 17V. The reason it is called a 12V solar panel is because it is designed to be used with 12V batteries. The 12V solar panel has to produce a higher voltage that will be reduced to around 12V by a charge controller for charging a battery.

What is Open Circuit Voltage (Voc)?

The is the maximum voltage from the solar panels with no load.

Does the Solar Panel Voc have to be less than the Maximum PV Input Voltage of the charge controller?

You must make sure your solar panels are connected properly for your charge controller to prevent damaging your charge controller.

For a 12V solar panel a typical Voltage Open Circuit (VOC) is 21.6V which is the maximum voltage produced by the solar panel. You have to make sure the VOC is less than the Maximum PV Input Voltage of your charge controller.

Often a PWM charge controller will have a Maximum PV Input Voltage of 23V so this would mean you have to connect multiple solar panels in parallel so you don't go over the max voltage limit. An MPPT inverter will often have a Maximum PV Input Voltage of 50V or more which will give you more flexibility in how you connect multiple solar panels.

Charge controller

Should you get a PWM or MPPT charge controller?

A MPPT charge controller is 30% more efficient than PWM but costs more.

The PWM charge controller typical has a max solar voltage input of 40 volts. If you connect multiple solar panels in series the voltage can become too high; therefore, often parallel is used to keep the voltage low but this increases the amps which requires thicker and more expensive wire.

The MPPT charge controller typically has a higher max solar voltage input than PWM. This allows using series to connect your solar panels keeping the amps low amps and using a thinner and cheaper wire. However, this increases the voltage which is a dangerous shock hazard.

What charge controller specifications do you need?

Battery Type: Select a charge controller that is capable of charging the type of battery you have. For example, for a LifePO4 battery get a charge controller that can charge a LifePO4 battery.
Battery Voltage: Select a charge controller that is rated to charge the voltage of your battery. Often solar charge controllers are rated for multiple voltages. For example, it might be rated for 12V/24V.
Max solar input voltage: Select a charge controller with a max solar input voltage that is greater than the solar voltage feeding into the controller. The total voltage from your solar panels depends on your solar panel voltage and how many panels are connected in series.
Charge Current: Select a charge controller with a charge current that is greater than the total amps from your solar panels.

How many solar panels can I connect to my charge controller?

Check your charge controller for the Max Solar Input Voltage and Charge Current it can handle.

In general, each 100 Watt solar panel outputs about 5 amps. Each 12 Volt solar panel has a Nominal Voltage of 12V but a VOC (Voltage Open Circuit) typical of 21 volts and VMP (Voltage Maximum Power) typical of 17 volts. However, check your solar panels specifications to find out for sure what these values are for your solar panel.

Calculate the current in amps for your solar panel by dividing the power in watts by the voltage in volts. For example, if the solar panel is rated at 175 watts and the voltage maximum power (VMP) is 23.6 volts.

175 watts ÷ 23.6 volts = 7.42 amps

Make sure amps and VOC are below your charge controllers rating to be safe.

Note: In this example, we only use one solar panel. If you have more than one solar panel connected in series or parallel you will need to make the proper adjustments because both the amps and voltage can be different depending on how you connected your solar panels.

What is Maximum PV Input Voltage?

The is the maximum voltage from the solar panels that the charge controller can take.

What is Maximum PV Input Power?

The is the maximum power from the solar panels that the charge controller can take.

Battery

What type of battery chemistry is best?

In 2024, Solid State batteries are starting to become available for DIY off-grid solar systems; however, it is not yet clear if they will be better and cheaper than LifePO4 batteries.
In 2024, Sodium Ion batteries are starting to become available for DIY off-grid solar systems; however, it is not yet clear if they will be better and cheaper than LifePO4 batteries. Some say the discharge curve is not anywhere near as good as LifePo4 batteries so keep that in mind when evaluating Sodium Ion batteries.
From 2023 to 2024, LifePO4 (lithium phosphate) batteries have been the most popular type of battery for DIY off-grid solar systems. The advantages of LifePO4 batteries are that they are maintenance free, have a longer lifespan than lead acid and lithium ion batteries, and are less likely to catch fire than lithium ion batteries. The disadvantages of LifePO4 batteries are that they are heavier and bulkier than lithium ion batteries.

What physical size of battery is best?

I would generally buy whatever is cheapest as long as the battery size fits your space. I would prefer Group 24 in most situations because it is the smallest.

Group 24: 10.5” L x 6.1875” W x 8.875” H.
Group 27: 11" L x 7.3" W x 9.3" H.
Group 31: 12.8" L x 6.8" W x 9.3" H.

What terminal or lug size does my battery have?

The most common terminal or lug size for a LifePo4 100 Ah battery is M8 (8mm or 5/16 inch); however, always check the specific specifications of your battery model to confirm the correct lug size.

For an M8 terminal, the M stands for metric and the number after, in this case 8, stands for the 8 mm diameter of the bolt.

1/4" M6
5/16" M8
3/8" –

Terminal Stud Hole Size Reference Chart

What battery voltage should I use?

The most common voltages for batteries for solar systems are 12V, 24V, and 48V. 36V can also be used but is uncommon. Voltages over 48V are currently uncommon.

One advantage of using a 12V battery is you can run 12V appliances directly from the battery without a DC to DC down converter. For example, many appliances for the car such as a tire Inflator plug directly into the cars 12V outlet so those can run from your 12V battery without a DC to DC down converter. With a 24V or 48V battery you would need a DC to DC down converter to get 12V.

A disadvantage of higher voltage batteries is the higher risk of shock.

The main advantage of higher voltage batteries is you can use thinner wires due to lower currents.

The example below shows that at the same 1800W, as the voltage increases from 12V to 48V, the amps decreases from 150A to 37.5A. You get the same power but at lower amps which allows using a thinner wire.

Amps (I) = Watts / Voltage
150A = 1800W / 12V
75A = 1800W / 24V
37.5A = 1800W / 48V

I recommend the following voltages as a general guide; however, you can always use a higher voltage if you prefer. As the power (watts) of your system goes up you almost have to switch to 48V because if you don't your wires have to be very big to handle the amps.

12V battery is recommended for up to 2000W.
24V battery is recommended for up to 4000W.
48V battery is recommended for up to 8000W.

How powerful of a battery do I need?

The more Ah a battery has determines how long it can run a load before needing to be recharged. In an EV car you could call this range or how many miles a car can drive before needing to be recharged.

The more Amp Hours (Ah) a battery has, the more power it has which is expressed in What Hours (Wh).

Often the battery only gives you the Ah but you can convert Ah to Wh.

To determine how much power your battery can produce you must know the Wh of your battery.

The example below shows how to convert Ah to Wh. In the example, I calculate a 12.8V 100 Ah battery has 1280 Wh of power.

Battery: 12.8V 100 Ah
Formula Convert Ah to Wh: Wh = Ah × V.
Answer: 1280 Wh = 100 Ah * 12.8V

As an example, if you are running a 1000W space heater for 1 hour it will use 1000Wh of power so with a 12V 100 Ah battery you would have a maximum of 1280 Wh so that could be enough to run a 1000W space heater for 1 hour or more. Keep in mind that if you are using an inverter to convert 12V DC to 120V AC that the inverter itself will use some power too while it is running the space heater for 1 hour.

What is the max watts or Max Discharge Current a battery can provide?

The max watts a battery can provide is determined by the batteries Max Discharge Current.

For example, if the battery has a Max Discharge Current of 100A then the max power you can get from a 12V battery is 12.8V x 100A = 1280 watts.

Smaller batteries have a smaller maximum discharge current but you can connect two batteries in parallel to double the Max Discharge Current. As an example, if you have two 12V batteries that each have a Max Discharge Current of 100A and you connect the batteries in parallel then you would have a max power of 2,560 watts available from the two batteries connected in parallel.

How to size the battery to the inverter?

Lead Acid: 100 Ah x 0.2C = 20A discharge rate
LifePo4: 100 Ah x 1C = 100A discharge rate

Inverter: 1000W / 12V = 83A

The inverter amps should be lower than the battery amps discharge rate.

1000W Inverter: How Many Batteries You Really Need

Adding Batteries in Series or Parallel

You can add one or more battery together and connect them in series or parallel.

Series: Add the voltage and take the lowest amps. Lower amps allow using thinner wire to connect panels to the charge controller.
Parallel: Add the amps and take the lowest voltage. This allows keeping the voltage lower so you don't go over the voltage max voltage input for your charge controller.

How long can a space heater run on battery?

A space heater typically uses 500, 750, 1000, or 1500 watts.

A 1000 watt space heater running for 1 hour will use 1000 Wh.

A 12 volt 100 Ah battery can produce 1280 Wh of power.

After running the space heater for 1 hour, 1000 Wh will be used from the battery leaving 280 Wh minus whatever the inverter itself used up during the hour. The inverter uses some power when it runs.

1280 Wh - 1000 Wh = 280Wh
280 - Inverter Wh used

This was just an example, generally space heaters are not used on battery power because of the high cost of batteries which currently are about $200 for a 12V 100 Ah battery.

What size battery do you need to run an entire house?

Typically to run an entire house you would need 5 to 10 kWh.

Solar battery cost: Why they're not always worth it

Inverter

Why do I need an inverter?

An inverter is needed because most home appliances run on 120V AC and most solar systems run on 12V, 24V, 36V, or 48V DC. If you wanted to buy all new appliances that run off of whatever DC voltage you are using then you would not need an inverter.

How much power in watts of an inverter do I need?

You need an inverter that provides enough power in watts for the appliance you want to run.

Some appliances such as a refrigerator also have a surge rating in watts so your inverter will also have to have enough surge rating in watts for your appliance..

Keep in mind that an inverter is not 100% efficient so just having an inverter turned on will some power known as idle consumption in watts.

Do I need a pure or modified sign wave inverter?

A pure sign wave inverter is more expensive than a modified sign wave inverter but should run all appliances just the same as the grid so to be sure everything will run correctly you should get a pure sign wave inverter.

A modified sine wave inverter is cheaper than a pure sign wave inverter but you risk some appliances like refrigerators, microwaves, electric pressure cookers, and compressors might not run as efficiently or might not run at all.

Unless you know a modified sine wave inverter will work for your application you are better off getting a pure sign wave inverter.

What is the Idle Consumption in Watts of an Inverter?

Generally 15 to 50 watts per hour but I would say about 25 watts on average. To find the exact amount you will need to check the specifications of your inverter.

Should the inverter be connected to the charge controller load output or directly to the battery?

The advantage of connecting the inverter to the charge controller load output is the charge controller load output has a Low Voltage Disconnect that will protect the battery from running too low.

Some batteries like lead acid and AGM batteries should not be drained too low before recharging because it can damage the battery so the charge controller Low Voltage Disconnect can protect your battery from draining too much.

LifePo4 batteries are safter to drain all the way but some people don't want to drain them more than 80%.

Some charge controllers might not offer enough power from the load output so by connecting to the battery you can get more power from your inverter. Just be aware that when you connect directly to the battery you do not have the Low Voltage Disconnect feature.

In addition, some charge controllers don't even have a load output so in that case you have to connect the inverter directly to the battery.

Some inverters have a low voltage shutoff so this is another way to get that feature if you want.

I think it is more common to connect the inverter directly to the battery.

Best Way To Wire Inverter? Battery vs. Charge Controller

What input voltage of inverter do I need?

You need an inverter that matches your battery voltage. As an example, if you are using a 12V battery you need a 12V inverter and if you are using a 24V battery you need a 24V inverter, etc.

What output voltage of inverter do I need?

Common output voltages are 110V to 120V. Inverters rated at 120V instead of 110V might be less likely to have compatibility problems.

How many Watts does a 120V electric outlet in the United States use?

In the United States, 120V outlets are either 15 or 20 amps.

120V 15 amp outlets

The 120V 15A outlet is the most common electric outlet in the United States.

120V 15 amp outlets use 14 AWG wire.

The 120V 15A outlet uses 1800 watts at 120 volts as shown by the V * A = W formula below.

V * A = W
120V * 15A = 1800W

This means that to run any home appliance such as a TV, Microwave, Toaster, or Space Heater one at a time you need an inverter that can supply at least 1800 watts continuously.

120V 20 amp outlets

There is also a 120V 20 amp outlet for use with large appliances like refrigerators and washing machines.

120V 20 amp outlets use 12 AWG wire.

The 120V 20A outlet uses 2400 watts at 120 volts as shown by the V * A = W formula below.

V * A = W
120V * 20A = 2400W

Reference:

How Do 15A and 20A Outlets Differ? What You Should Know

How many watts do I need to run the average appliance?

Note these are rough estimates for an average appliance so you will need to check how many watts your appliance uses to be sure what the correct value is for you appliance.

Standard refrigerator: 300 to 800 watts.
Mini refrigerator: 50-180 watts.
Window air conditioner: 500 to 800 watts.
2 slice toaster: 700 to 1100 watts.
Small Microwave: 500 to 800 watts.

What is the max wattage a space heater or hair dryer uses?

Both a space heater and hair dryer are designed to be used on a standard 1800 watt outlet. A space heater is only allowed 1500 watts max out of 1800 watts because it is used continuously. A hair dryer is allowed the full 1800 watts max out of 1800 watts since it is not intended to be used continuously.

What size will run a full size refrigerator?

I have the full size refrigerator below and on the inside it says it is 6.5 amps. 6.5 amps x 120 volts = 780 watts.

Whirlpool 18.2 cu. ft. Top Freezer Refrigerator in White Model # WRT318FZDW

According to Microsoft copilot below in bold.

A 6.5 amp refrigerator would typically require an inverter with a capacity of at least 1000 watts to function properly, as you need to factor in the startup surge when the compressor kicks on, which can be significantly higher than the running wattage; this translates to around 2-3 times the average running power.

In my opinion, I would want at least a 1500 watt 3000 watt surge inverter for a 780 watt refrigerator.

What terminal or lug size does my inverter have?

The typical terminal or lug size for inverters around 1000 watts and above is 3/8 inch; however, always check the specific specifications of your battery model to confirm the correct lug size.

What is a Low Frequency Inverter?

A Low Frequency Inverter has a larger transformer and are heavier, can handle larger surges, has a higher idle current, are more reliable., and cost more. Most inverters are not Low Frequency Inverters because they cost more.

What is an inverter pre-charge resistor?

An inverter pre-charge resistor is used to prevent sparks when connecting an inverter to the battery. A typical value is 25W 30 Ohms that you use in series with the positive battery cable of the inverter when connecting to the battery and then remove after a second when it is pre-charged and then connect the inverter cable directly to the battery.

What is a DIY grid-tie inverter?

A grid-tie inverter takes power from a solar panel and pumps it into your houses electrical system while your grid power is live.

This is what a typical professionally installed solar system does; however, those generally require a permit to install and approval of your power company.

However, they do sell grid-tie inverters that you can install yourself (DIY) without a permit. Below is one example, of a grid-tie inverter you can buy from Amazon.

Y&H 1000W Grid Tie Inverter Stackable MPPT Pure Sine Wave DC30-45V Solar Input AC90-140V Output for 24V 30V 36V PV Panel

The grid-tie inverter takes DC input from your solar panel and outputs 120V AC that you plug directly into your houses live electrical outlet. It feeds power into your houses electrical system so the power it produces will be used before using any grid electricity. Warning never plug a normal inverters 120V AC output into your houses live electrical outlet.

Are DIY grid-tie inverters legal?

As of 2025, Utah has made grid tie inverters legal but check that the grid tie inverter you buy is approved for use in your area if you buy one.

This Solar Panel is ILLEGAL (except in Utah)

Anti-islanding

Most grid-tie inverters have a feature called anti-islanding. Anti-islanding shuts off your grid-tie inverter if your grid power does down so it does not feed power into the grid during a power outage to protect line workers from getting shocked.

Sync 120V 60 Hz Frequency to Grid

The grid-tie inverter syncs the 120V 60 Hz frequency to match your grid power.

Back Feeding

Back feeding the grid is generally not allowed by power companies. The power company might be able to detect if you are back feeding power and if so might disconnect your power if you don't stop it. Smart meters can inform the power company if you are back feeding but mechanical meters can't. If you can keep the power generated less than what you are using it won't back feed. Some grid-tie inverters have current sensors that can connect to your breaker panel to detect how much current you are using and limit the current generated so it won't back feed. If you can get this to work it would not back feed.

The video below shows a grid-tie inverter setup to monitor the total power being used by the house so it will never back feed power to the grid.

Reference: https://www.youtube.com/watch?v=stJV-i0CpNQ

Conclusion

The problem with using a grid-tie inverter is the power company might not allow it, might disconnect your power if they detect it, or might charge you a fee if you feed back electricity to the grid.

The bottom line is that there are no DIY grid-tie inverters that I know of that are approved by the government and power companies where you can use it with a guarantee you won't get in trouble. The advantage of off-grid is that you can't run into problems with the power company or government.

Although the grid-tie inverter concept is great if it works I am not going to risk trying it. If you try a DIY grid-tie inverter try it at your own risk.

If there was a power company and government approved DIY grid-tie inverter available at a reasonable price that I could use without a permit or asking permission of the power company or government I would try it. The power companies and government have made no effort to make this happen so I think they just want you to get the standard professionally installed grid-tied solar system that requires a permit.

This document does not cover using a DIY grid-tie inverters but I just wanted to mention them so you know about them.

Solar System Wiring

10 AWG wire (10-gauge) can handle 30 amps. Often used to connect solar panels to the charge controller.
12 AWG wire (12-gauge) can handle 20 amps. A 120V 20 amp outlet uses 12 AWG wire.
14 AWG wire (14-gauge) can handle 15 amps. A 120V 15 amp outlet uses 14 AWG wire.

Can household extension cords be used instead of solar wires?

Solar wires can handle higher voltages than typical household extension cords so even if the gauge wire is the same it is not recommended to use household extension cords instead of solar wires.

Formulas

W (Watts) =V (Voltage) × I (Current)
I (Current) = W (Watts) ÷ V (Voltage)

Solar System Operation

Powerup Sequence

Charge Controller

Connect the battery to the charge controller.
Connect the solar panels to charge controller.

Inverter

Connect the battery to the inverter. Warning, there might be a spark which is normal.
If the inverter has a power switch turn the inverter on.

Powerdown Sequence

Charge Controller

Disconnect the solar panels from the charge controller.
Disconnect the battery from charge controller.

Inverter

If the inverter has a power switch turn the inverter off.
Disconnect the battery from the inverter.

Design Tips

300 watts of solar panels is typically enough to charge a 100 Ah battery in a day; however, it depends on how much sun you get. If you don't get enough sun it will take longer or you will need more solar panels.
Recommended battery voltage is; 12V battery for up to 2000W; 24V battery for up to 4000W; 48V battery for up to 8000W.
Decide on your battery voltage first, such as 12V, 24V, 36V, or 48V and buy the inverter and charge controller that can handle that voltage.
You can get a charge controller that can handle more than one voltage which could be useful if you ever want to increase your systems battery voltage. Some can handle 12, 24, 36, or 48 volts.
In the future, if you want to change the battery voltage from 12V to 24V or 48V you will need to buy a new inverter because they do not make inverters that can operate at multiple voltages.
Remember there is always some loss in the inverter because they are not 100% efficient. Typically an inverter can use 25 watts when idle. To save battery power you can turn off your inverter when you are not using it. Some inverters can automatically turn themselves off when not in use and turn back on where there is a load.
In most cases you should get a Pure Sine Wave inverter because it is capable of running any appliance. To save money get a Modified Sine Wave inverter only if you know it will run every load that you want to run.
Batteries have a maximum discharge rate. For example, a 12.8V 100 Ah LifePo4 battery generally has a maximum discharge rate of 100 amps or 1280 watts so this means that the most you can get out of it is 1280 watts so if you use a 2000 watt inverter with that battery you can't ever get 2000 watts output. However, if you connect two 12.8V 100 Ah in parallel then you could get more power.
48V is the highest common voltage used in solar systems for residential homes. Also 48V is the nominal voltage so for batteries actual voltage could be 51.2. It is possible that in the future higher voltages might become more common but right now I wouldn't try to go higher than a 48V solar system. If trying to create a solar system with voltages higher than 48V there are many design issues thta need to be taken into account. In addition, higher voltages are more dangerous.

Design Questions

How many solar panels and batteries are needed to run a standard refrigerator?

My estimates will only account for exactly what you need assuming no days without sun. If you want to add a safety factor for days without sun you can add that later. For example, if you want a safety factor of 3 days without sun then take the results and multiple times 3.

Estimate of Wh used

In this estimate I am using the Mora 18 cu. ft. Top Freezer Refrigerator from Costco that cost $579.99. I am using the Energy Guide estimate of 403 KWh per year.

403 KWh per year / 12 = 33.58 KWh per month / 30 = 1.12 KWh per day = 1120 Wh per day.

The inverter will use power just while running idle and not running a load. A 1000 watt inverter can use about 20 watts of power continually. This is 20 watts x 24 hours = 480 Wh per day.

Refrigerator: 1120 Wh per day
Inverter: 480 Wh per day
Total: 1600 Wh per day

Estimate of battery in Ah needed

1600 Wh / 12.8V = 125 Ah

So you need a 12.8V 125 Ah. I am going to round this down to 12.8V 125 Ah because that is a common size battery. If it turns out not to be enough you would need to add another 12.8V 100 Ah battery.

Estimate of solar panels needed in watts

You can use the website below to find the lowest average sun hours per day for the year in your area or you can just guess. A good guess would be 4.

https://pvwatts.nrel.gov/

I am going to use 4 hours of sun per day on average.

1600 Wh / 4 hours of sun = 400 watts

So you need 400 watts of solar panels.

Conclusion

To run a standard refrigerator you will need:

Solar panels: 400 watts
Battery: 12V 100 Ah LifePo4

Note these values don't include a safety factor for days without sun.

How many solar panels and batteries are needed to run a mini refrigerator?

My estimates will only account for exactly what you need assuming no days without sun. If you want to add a safety factor for days without sun you can add that later. For example, if you want a safety factor of 3 days without sun then take the results and multiple times 3.

Estimate of Wh used

In this estimate I am using the Danby 3.3 cu ft Compact All Refrigerator from Costco that cost $229.99. I am using the Energy Guide estimate of 36 KWh per year. I am using my cost of electricity in California of about 0.50 per KWh.

The inverter will use power just while running idle and not running a load. A 1000 watt inverter can use about 20 watts of power continually. This is 20 watts x 24 hours = 480 Wh per day.

36 KWh per year / 12 = 3 KWh per month / 30 = 0.1 KWh per day = 100 Wh per day.

Refrigerator: 100 Wh per day
Inverter: 480 Wh per day
Total: 580 Wh per day

Estimate of Ah battery needed

580 Wh / 12.8V = 45.3 Ah

So you need a 45.3 Ah battery. I am going to round this up to 100 Ah which is more than you need but I think the 100 Ah battery size is more popular. If you want to save money you can go with a 50 Ah battery.

Estimate of solar panels needed in watts

You can use the website below to find the lowest average sun hours per day for the year in your area or you can just guess. A good guess would be 4.

https://pvwatts.nrel.gov/

I am going to use 4 hours of sun per day on average.

580 Wh / 4 hours of sun = 145 watts

So you need 145 watts of solar panels. I am going to round this up to 200 watts.

Conclusion

To run a mini refrigerator you will need:

Solar panels: 200 watts
Battery: 12V 100 Ah LifePo4

Note these values don't include a safety factor for days without sun.

Solar System Tips

LifePO4 batteries should not be charged when temperatures are at or below freezing to prevent battery damage. Some batteries come with a low temperature shut-off to protect the battery from charging during freezing temperatures. Some batteries even have built in heaters to keep the battery warm in freezing temperatures.
The wires running from the battery to the inverter should be as short as you can make them so that power loss from the wires is kept to a minimum. This is even more important with lower voltage batteries (i.e. 12V) because they run at higher amps.

Solar System Future Trends

Using EV car batteries for home battery storage is a trend likely to become common in the future. EV cars have powerful batteries capable of running an entire house and if you are going to have an EV car anyway it is like getting a free battery for your home solar system.
In 2024, Solid State batteries are starting to become available for DIY off-grid solar systems; however, it is not yet clear if they will be better and cheaper than LifePO4 batteries.
In 2024, Sodium Ion batteries are starting to become available for DIY off-grid solar systems; however, it is not yet clear if they will be better and cheaper than LifePO4 batteries. Some say the discharge curve is not anywhere near as good as LifePo4 batteries so keep that in mind when evaluating Sodium Ion batteries.

Solar System Component Parts

This is a parts list of Solar System Component Parts. This covers anything from individual components to solar generators. Basically this covers all parts except wiring and hardware.

These parts are used for the Solar System Component Configurations below.

None of these links are affiliate links.

All of these parts are picked by me and are parts that I might consider buying myself but aren't tested or being recommended by me so please do your own research when selecting parts.

Prices are subject to change.

Solar Panels Rigid Mono-facial

Solar Panels Rigid Bifacial

100W

ECO-WORTHY 200 Watt Bifacial Solar Panel 2pcs 100 Watt 12 Volt Monocrystalline Solar Panel Module Off Grid PV Power for Home, Camping, Boat, Shed Farm, RV ($116.45 2/1/2025)

200W

400W

Hyperion By Runergy 400w Bifacial Solar Panel (Black) | Up to 500W with Bifacial Gain (10 × $100.00 = $1000.00 12/28/2024) (Minimum purchase 10.)

Solar Panels Flexible Mono-facial

100W

HQST 100W 12V Flexible Monocrystalline Solar Panel,9BB 100 Watts Mono Solar Panel,Polished PET Coating,23% High Efficiency Module PV Power,IP67 Waterproof for RV Camper Van Boat Yacht Cabin Shed ($69.99 - $10 coupon = $59.99 1/29/2025)

Solar Panels Portable

110W

DOKIO 110w 18v Portable Foldable Solar Panel Kit (21x28inch, 5.9lb),Solar Controller 2 USB Output to Charge 12v Batteries/Power Station (AGM, Lifepo4) Rv Camping Trailer Emergency Power ($129.99 - $50 coupon = $79.99 2/5/2025)

Charge Controllers

PWM

MPPT

10A MPPT Waterproof Charge Controller ($58.99 1/4/2025)
SOLPERK 10A 12V MPPT Solar Charge Controller, Waterproof Intelligent Portable Controller IP67 Solar Panel Controller Solar Controller for AGM, Gel, Flooded and Lithium Battery ($19.99 - $5 coupon = $14.99 1/4/2025)
ATEM POWER 20A 12V/24V MPPT Solar Controller Selecting Battery Type Activate Lithium Battery Intelligent Solar Controller Compatible with Lead Acid, AGM, Gel, Calcium and LiFePO4 Battery ($29.99 2/2/2025)
20A MPPT Solar Charge Controller 12V/24V Auto Adaptive-Dual Fans-Dual 5V/3A USB Output,for AGM,Gel,Flooded and Lithium ($39.98 12/31/2024)
BougeRV MPPT Solar Charge Controller 40A, with Remote APP Control, Backlit LCD Display, Temperature Sensor, 12V/24V/36V/48V Battery Regulator, for LiFePO4, SLD, AGM, FLD, Gel Battery, Negative Ground ($159.99 - $40 coupon = 119.99 12/24/2024)

Batteries 12V

Warning batteries on Amazon often do not have free shipping so always check how much the delivery charge is to find the total price.

12V 100Ah (No Low Temperature Protection)

12V 100Ah (Low Temperature Protection)

12V 100Ah (Low Temperature Protection, Bluetooth)

Batteries 24V

Warning batteries on Amazon often do not have free shipping so always check how much the delivery charge is to find the total price.

24V 50Ah (No Low Temperature Protection)

25.6V 50Ah LiFePO4 Battery, Built with 100A BMS, Max. 2560W Power, BCI Group 24 Size Lithium Battery, Support in 2 Series/4 Parallel, Perfect for Trolling Motor, RV, Camping, Solar Home ($229.99 - $20 coupon = $209.99 1/5/2025)

Batteries 48V

Warning batteries on Amazon often do not have free shipping so always check how much the delivery charge is to find the total price.

48V 25Ah (No Low Temperature Protection)

48V 25Ah LiFePO4 Battery, BCI Group 24 Lithium Battery, Deep Cycle Battery with 50A BMS, 2560W Load Power, Up to 15000 Cycles & 10-Year Lifespan for Trailer RV, Marine, Camping, Solar System ($269.99 - $40 coupon = $229.99 1/5/2025)

48V 100Ah (No Low Temperature Protection, Bluetooth)

ECO-WORTHY 48V 100Ah LiFePO4 Lithium Battery, 5.12kWh Capacity, Server Rack Battery with Bluetooth, 6000 Cycles, 3U Chassis, Perfect for Off-Grid, Solar, Backup Power ($999.99 - $110 coupon = $889.99 2/17/2025) YouTube

Inverters 12V

12V 500W

12V 600W

12V 800W

WZRELB 800W Pure Sine Wave Inverter 12V DC to 110V 120V AC Power Converter with LED Display, Off-Grid Portable Power Inverter with 2 AC Outlets for Home, RV, Truck, Camping ($59.71 2/11/2025)

12V 1000W

12V 1200W

DongJin 1200W Power Inverter Pure Sine Wave Inverter DC 12V to AC 110V 120V Converter for Home RV Camping 1200 Watt Power Inverter for Vehicles Car with LED Display,USB,Type-C,Remote Control,AC Outlet ($54.14 1/15/2025)

12V 1500W

BELTTT 1500W Pure Sine Wave Inverter 12V to 120V AC, Car Power Inverter 12V to 110V Converter for RV, Truck, Solar, Off-Grid with Dual AC Socket, 5V 2.1A USB, Surge 3000W, Smart LCD Display ($109.99 - $10 coupon = $99.99 12/25/2024)
Pure Sine Wave 1500W Power Inverter DC 12V to AC 110V 120V FCC Approved with Dual GFCI Outlets LCD Display Remote Controller & Dual 4.8A USB Ports LEESKY YouTube (GFCI Outlets) ($159.96 11/5/2024)

12V 1600W

Pure Sine Wave Inverter 1600 Watts Inverter DC 12V to AC 110V with Remote Controller & LCD Display and 4 AC Outlets 4 USB Ports for Car Truck Solar Power & Emergency (Wireless Remote) ($139.99 - $10 coupon = $129.99 12/24/2024)

12V 1800W (120V x 15A Outlet)

12V 2000W

2000W Pure Sine Wave Inverter 12V DC to 110V AC Converter 120V 4000W Peak for Vehicle/Home/RV/Truck Off-Grid Solar Power Inverter with USB & Type-C Port, 2 AC Outlets & LCD Display Remote Controller ($129.99 12/29/2024)
2000 Watt Pure Sine Wave Inverter 12V DC to 110V/120V AC Car Converter with USB & Type-C Fast Charging Ports, 2 AC Outlets, LCD Display Remote Controller for RV Truck Off-Grid Solar Power Inverter ($159.99 - $30 coupon = $129.99 12/24/2024)
VEVOR Pure Sine Wave Inverter, 2000 Watt, DC 12V to AC 120V Power Inverter with 2 AC Outlets 2 USB Port 1 Type-C Port, LCD Display and Remote Controller for Medium-Sized Household Equipment, CE FCC (Wireless Remote) ($179.99 - $20 coupon = $159.99 11/17/2024)
Xijia 2000W Pure sine Wave Power Inverter (Peak Power 4000W) dc 12v to 110v/120V ac 60HZ LCD-Display Bluetooth Remote Control,2 AC Outlets for RV, Camping, Boat,Outdoor (Bluetooth) ($166.00 12/12/2024)
Power Inverter 2000 Watt Pure Sine Wave Inverter DC 12V to AC 110V 120V FCC Approved with Digital LCD Display and 2 GFCI AC Outlets Dual 4.8A USB Ports & Remote Controller LEESKY (GFCI Outlets) ($199.99 12/4/2024)
BougeRV Pure Sine Wave Inverter 2000W Convert DC 12V to AC 110V, Built-in Bluetooth for Mobile APP, ON/Off/ECO Operating Modes, for Off-Grid Solar Power System, RV, Home Backup Power (Idle Auto Shutoff) ($369.99 12/4/2024)

12V 2200W

2024 New Upgraded 2200 Watts Pure Sine Wave Inverter, 12V DC to 110V AC Power Inverter with 4 AC Outlets, USB Port, Type-C Port for Truck, Vehicle, Power Outage, Remote Control with LCD Screen (Low Voltage Shutdown) ($189.99 - $20 coupon = $169.99 12/25/2024)

12V 2300W

2300W Power Inverter,12V DC to AC 110V120V Peak Power 4600W with 2AC Outlets and 2.4USB Port,LCD Display Car Inverter for Power Converter Outdoor Activities,Emergency,Vehicles Truck RV Solar System ($127.48 12/25/2024)

12V 2400W (120V x 20A Outlet)

12V 2500W

2500 Watt Modified Sine Wave Power Inverter, 12V DC to AC 110V/120V (Peak) 5000W Converter 3 Outlet Car Inverter with Remote Control and LED Display 3.4V USB Port (Wireless Remote) ($149.99 - $10 coupon = $139.99 12/25/2024)

Inverters 24V

24V 3000W

POWLAND 3000W Solar Inverter, Pure sine Wave Inverter, 24V to 110V/120V, Built-in 60A MPPT Controller, Suitable for Homes, RVs, and can be Used with Lithium Lead-Acid Gel Battery Off-Grid Systems ($349.99 1/8/2025)

Inverters 48V

48V 2000W

2000W Power Inverter 48V DC to 110V AC 60HZ Pure Sine Wave Converter with LED Display for Off Grid Solar System ($159.00 - $20 coupon = $139.00 1/5/2025)

48V 2500W

New 48V 2500 Watts Pure Sine Wave Inverter, 48V DC to 110V AC Power Inverter with 4 AC Outlets, USB Port, Type-C Port for Truck, Vehicle, Power Outage, Remote Control with LCD Screen ($219.99 - $20 coupon = $199.99 1/5/2025)

Inverter Pre-charge Resistor

smseace 5pcs 25W 30ohm Ceramic Cement resistors ±5% Tolerance Cement resistors Used in Computer, TV Set, Apparatus ($7.99 1/22/2025)

AC Battery Charger

Battery Box

Fireproof

Box

12V

12V Battery Box Outdoor Portable Multifunction Trolling Motor Battery Tray Cases for Marine Boat RV Camping Travel Lead acid AGM Lithium LiFePO4 Battery Plastic Boxes(Battery not Include) ($79.99 1-3-2025)
SUNAPEX Smart Battery Box 12V/24V Power Center - Multi Ports & Circuit Breaker for Trolling Motor, Marine,RV & Solar Panel (Pro,Battery Not Included) ($99.99 - 20% = 79.99 12/24/2024)
ALL-TOP Smart Battery Box, 12V Marine Case w/ 50AMP Connectors, Multi Ports & Circuit Breaker for Trolling Motor, RV & Solar Panel, Battery Not Included ($89.99 - 10% = 80.99 12/24/2024)

12V, Charge Controller, Inverter

Licitti 1000W AC Battery Box ($168.00 + $55.00 Shipping: = $223.00 11/13/2024)
Licitti 2000W AC Battery Box ($438.00 + UPS Shipping: $75.00 = $513.00 12-1-2024)
Licitti CyberBox 3000 Portable Power Station ($1,565.00 12-1-2024)

Power Distribution Box

Solar System Kits

100W

WEIZE 100 Watt 12 Volt Solar Panel Starter Kit, with 10A PWM Charge Controller, High Efficiency Monocrystalline PV Module for Home, Camping, Boat, Caravan, RV and Other Off Grid Applications ($59.99 8/8/2024)

Nicesolar 100W 12V Bifacial Solar Panel kit Monocrystalline Off Grid System Battery Charger for RV Boat Trailer Cabin Garden Shed Home 20A Charge Controller for Lead-Acid Lithium LiFePO4 Battery ($77.45 8/8/2024)

200W

400W

ECO-WORTHY 1.6KWH Complete Solar Panel Kit 400W 12V for RV Off Grid: 4*100W Bifacial Solar Panel + 40A MPPT Controller + 2*12V 100Ah Lithium Battery + Upgraded 2000W Power Inverter + Bluetooth Module ($1,479.99 12/27/2024)

Solar Generators

600W

OUPES Exodus 600 Portable Power Station 600W, 256Wh Solar powered Generator with 2 AC Outlets(1200W peak), Full Recharge in 1 Hrs LifePO4 Battery Generator for Camping ($189.00 - $50 coupon = $139.00 1/30/2025)

1200W

OUPES Exodus 1200 Portable Power Station 1200W (3600W Surge) – 992Wh LiFePO4 Solar Generator with Dual PD 140W Type-C, Smart App Control, UPS, Ideal for Home, Camping, and Blackout Emergency Backup ($699.99 - 50% coupon = $350.00 1/30/2025)

1800W

PECRON E1000LFP Portable Power Station 1800W 1024Wh PRE-ORDER ($399.00 - $20 YouTube coupon = $379.00 3/21/2025)

Solar System Wiring Parts

This is a parts list of Solar System Wiring Parts. This covers anything from wiring to hardware

These parts are used for the Solar System Wiring Configurations below.

Switches

Master Switch

Ampper Battery Switch, 12-48 V Battery Power Cut Master Switch Disconnect Isolator for Car, Vehicle, RV and Boat (On/Off) ($11.99 1/3/2025)

Isolator switch

This can go between the solar panels and the charge controller to turn off power from the solar panels.

DC Miniature Circuit Breaker, 2 Pole 1000V 63 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C63 ($15.98 12/21/2024)

Cables

Solar Panel To Charge Controller Extension

Choose the cable length you need to go from your solar panels to your charge controller. Most solar panels have MC4 connectors; therefore, the MC4 connector plugs into your solar panels MC4 connector and the other end is bare wire that connects to your charge controller.

You can buy wire with a MC4 connector already connected or buy bare wire and connectors and put the connector on the wire yourself. If you are going to put on the MC4 connectors yourself a MC4 crimping tool would make the job easier.

One MC4 connector

No connector

BougeRV 20 Feet 10AWG Solar Wire Solar Panel Wire Pure Copper Wire (20FT Red + 20FT Black) ($19.99 12/22/2024)
BougeRV 30 Feet 10AWG Solar Wire Solar Panel Wire Pure Copper Wire (30FT Red + 30FT Black) ($19.99 12/22/2024)
BougeRV 50 Feet 10AWG Solar Wire Solar Panel Wire Pure Copper Wire (50FT Red + 50FT Black) ($64.99 12/22/2024)

MC4 Connectors

BougeRV 12 PCS Solar Connectors with Spanners Solar Panel Cable Connectors 6 Pairs Male/Female(10AWG) ($11.99 12/22/2024)

MC4 Crimping Tool

Solar Crimping Tool for Solar Panel Cable with 12 Pairs Solar Connectors, 1PCS Solar Crimper, 2 PCS Spanner Wrench, Crimper Tool for 2.5/4/6mm² Solar PV Wire ($20.99 2/3/2025)

Charge Controller To Battery

Battery To Inverter Cable

Generally an inverter will come with a cable so you don't need to buy one.

2 AWG Gauge Red + Black Pure Copper Battery Inverter Cables Solar, RV, Car, Boat 12 in 5/16 in Lugs ($13.82 12/22/2024)

Solar Panel To Solar Panel In Parallel

BougeRV Solar Connectors Y Branch Parallel Adapter Cable Wire Plug Tool Kit for Solar Panel ($7.99 2/3/2025)

Wire Battery Box

Wire

To connect a 12V 2000W inverter to the battery you need a 1/0 AWG cable but for a 48V 2000W inverter you need 10 AWG.

Bus Bars

MOFEEZ Power Distribution Block Bus Bar, 4 x 5/16" Posts, 6 x #8 Screws Terminals, Max 48V 250A (Pair, Red & Black) $22.39

Power Outlets

Power Distribution Box

Power Distribution Box, 110V High Current Wall Mount Electrical Box with NEMA 5-20 Power Outlet Pane,IP54 Electrical Breaker Socket Distribution Box for Construction Sites, workshops and Factories ($79.99 7/20/2025)

Fuses

Circuit Breakers

3 Pack 100 Amp Circuit Breaker Manual Reset Car Marine Trolling Motors Boat ATV Manual Power Protect for Audio System Fuse 12V-48VDC $24.99

Fans

Anderson Connectors

Extension Cords

Iron Forge Cable Lighted Outdoor Extension Cord 200 ft - 10 Gauge 15 Amp Heavy Duty Power Extension Cords - SJTW - Great for Major Appliances, Power Tools, Garden Supplies - Yellow ($289.99 1/11/2025)

Solar System Component Configurations

Below are various sample Solar System Component Configurations using the Solar System Component Parts from above.

My First Solar System 12V-100Ah $250.75 (Solar Panel Not Included)

This is a possible configuration for my first solar system but it is not finalized yet.

I'm planning on having two solar systems, a lower power 12V solar system and a higher power 48V system. The reason I want two solar systems is I want the 12V system for running 12V devices directly from the battery and the 48V system for running 120V AC devices. I want to run 12V devices designed to be run from a car cigarette lighter from the 12V system so I don't have to use a DC to DC downconverter. I want a 48V system to run the 120V AC inverter because it will be able to use thinner wire while providing more power. I plan to create the low power 12V system first.

Solar Generator 600W $139.00 (Solar Panel Not Included)

OUPES Exodus 600 Portable Power Station 600W, 256Wh Solar powered Generator with 2 AC Outlets(1200W peak), Full Recharge in 1 Hrs LifePO4 Battery Generator for Camping ($189.00 - $50 coupon = $139.00 1/30/2025)

Battery Box 1000W 12V-100Ah $236.32 (Solar Panel Not Included)

Licitti Battery Box 1000W MPPT 12V-100Ah $382.99 (Solar Panel Not Included)

Licitti 1000W AC Battery Box ($168.00 + $55.00 Shipping = $223.00 11/13/2024)
Elefast 12V 100Ah Bluetooth LiFePO4 Lithium Battery, BCI Group 24,Low Temperature Protection Up to 20000 Cycles, 1280Wh Energy LiFePO4 Battery in Small Size, Perfect for RV, Solar, Trolling Motor ($149.99 + $10 delivery = $159.99 11/24/2024) (Low Temperature Protection/Bluetooth) YouTube

Solar Generator 1200W $315.00 (Solar Panel Not Included)

OUPES Exodus 1200 Portable Power Station 1200W (3600W Surge) – 992Wh LiFePO4 Solar Generator with Dual PD 140W Type-C, Smart App Control, UPS, Ideal for Home, Camping, and Blackout Emergency Backup ($699.99 - 50% coupon - 5% YouTube code Ouroupes = $315.00 1/31/2025)

Solar System 12V 200Ah 2000W $553.9 (Solar Panel Not Included)

This is a sample of parts that can be ordered to build a 12V 2000W Solar System.

40A MPPT charger controller
2000W Inverter
12V 100Ah battery
12V 100Ah battery

Equipment

This system uses poly solar panels so save money. If you want to spend more you can get mono solar panels instead.
Connect the two 12V 100 Ah batteries in parallel to run the full 2000W of the inverter.

BougeRV MPPT Solar Charge Controller 40A, with Remote APP Control, Backlit LCD Display, Temperature Sensor, 12V/24V/36V/48V Battery Regulator, for LiFePO4, SLD, AGM, FLD, Gel Battery, Negative Ground ($159.99 - $40 coupon = 119.99 12/24/2024)
12V 100Ah Mini LiFePO4 Lithium Battery, Built-in 100A BMS,1280Wh, Up to 15000 Cycles 10-Year Lifespan Perfect for RV, Solar, Marine, Golf Cart,and Home Energy Storage ($136.96 2/1/2025) YouTube
12V 100Ah Mini LiFePO4 Lithium Battery, Built-in 100A BMS,1280Wh, Up to 15000 Cycles 10-Year Lifespan Perfect for RV, Solar, Marine, Golf Cart,and Home Energy Storage ($136.96 2/1/2025) YouTube
VEVOR Pure Sine Wave Inverter, 2000 Watt, DC 12V to AC 120V Power Inverter with 2 AC Outlets 2 USB Port 1 Type-C Port, LCD Display and Remote Controller for Medium-Sized Household Equipment, CE FCC (Wireless Remote) ($179.99 - $20 coupon = $159.99 11/17/2024)

Hybrid Solar System 24V 50Ah 3000W $559.98 (Solar Panel Not Included)

This is a sample of parts that can be ordered to build a 24V 3000W Solar System.

60A MPPT charger controller
24 3000W Inverter
24V 50Ah battery

Equipment

Solar System 48V 25Ah 2500W $549.97 (Solar Panel Not Included)

This is a sample of parts that can be ordered to build a 48V 2500W Solar System.

This 48V solar system provides a max of 2560W from a single 48V battery. In addition, using a 48V battery means you can use thinner and cheaper wire.

40A MPPT charger controller
48V 2500W Inverter
48V 25Ah battery

For a 48V charge controller typically at least 3 or 4, 12V 100W solar panels are required to meet the minimum voltage of the charge controller.

Equipment

BougeRV MPPT Solar Charge Controller 40A, with Remote APP Control, Backlit LCD Display, Temperature Sensor, 12V/24V/36V/48V Battery Regulator, for LiFePO4, SLD, AGM, FLD, Gel Battery, Negative Ground ($159.99 - $40 coupon = 119.99 12/24/2024)
New 48V 2500 Watts Pure Sine Wave Inverter, 48V DC to 110V AC Power Inverter with 4 AC Outlets, USB Port, Type-C Port for Truck, Vehicle, Power Outage, Remote Control with LCD Screen ($219.99 - $20 coupon = $199.99 1/5/2025)
48V 25Ah LiFePO4 Battery, BCI Group 24 Lithium Battery, Deep Cycle Battery with 50A BMS, 2560W Load Power, Up to 15000 Cycles & 10-Year Lifespan for Trailer RV, Marine, Camping, Solar System ($269.99 - $40 coupon = $229.99 1/5/2025)

Solar System 48V 100Ah 2500W $1,274.93 (Solar Panel Not Included)

This is a sample of parts that can be ordered to build a 48V 2500W Solar System.

This 48V solar system provides a max of 2560W from a single 48V battery. In addition, using a 48V battery means you can use thinner and cheaper wire.

40A MPPT charger controller
48V 2500W Inverter
48V 100Ah battery

For a 48V charge controller typically at least 3 or 4, 12V 100W solar panels are required to meet the minimum voltage of the charge controller.

Equipment

BougeRV MPPT Solar Charge Controller 40A, with Remote APP Control, Backlit LCD Display, Temperature Sensor, 12V/24V/36V/48V Battery Regulator, for LiFePO4, SLD, AGM, FLD, Gel Battery, Negative Ground ($159.99 - $40 coupon = 119.99 12/24/2024)
New 48V 2500 Watts Pure Sine Wave Inverter, 48V DC to 110V AC Power Inverter with 4 AC Outlets, USB Port, Type-C Port for Truck, Vehicle, Power Outage, Remote Control with LCD Screen ($219.99 - $20 coupon = $199.99 1/5/2025)
48V 100AH Lithium LiFePO4 Battery, Built-in 100A BMS, with Touchable Smart Display & Mobile APP, Max. 4800W Power Output, 5000+ Cycles, Perfect for Solar System &Off-Grid Applications ($934.95 2/9/2025)

Solar System Wiring Diagrams

There are four basic ways to wire a solar system and each is show here with wiring diagrams.

One Solar Panel Wiring Diagram
Two Solar Panels In Parallel Wiring Diagram
Two Solar Panels In Series Wiring Diagram
Four Solar Panels In Series Parallel Wiring Diagram

For simplicity I only show a maximum of two solar panels for series and parallel in the wiring diagrams but you can add more than two if you want. For example, I show only two solar panels in parallel but you can add more solar panels in parallel if you want. In addition, I only show two solar panels in series but you can add more solar panels in series if you want. However, keep in mind that you must keep the voltage and current within the range limits of the solar charge controller you are using and use the proper wire size.

Figure 1: One Solar Panel Wiring Diagram $19.97

Figure 1, shown below, is a wiring diagram that shows the minimal way to wire a solar systems with one solar panel. If you want to add additional features such as power switches, fuses, bus bars and more solar panels it will take more wiring.

The Load is optional and not all charge controllers have a Load output so the inverter Load wiring is not included here.

The inverter is optional and only needed if you want 120V AC power. Most inverters come with wires so none are included here; however, often the wires provided are underrated when running the inverter at full power. If the wires provided with your inverter are underrated for powering your inverter at full power and you want to run your inverter at full power you would need to buy better wires.

You most likely could make the wiring cheaper if you buy the wire and connectors separate and put the connectors on yourself but then you need to buy a crimping tool which is an extra one time costs. If you just want one set of wires it might be cheaper to buy the wire with the connectors already installed but if you want to make multiple wire sets in the long run it might be cheaper to make them yourself.

Part #1: Solar Panel To Charge Controller Extension

Professional Connection 10AWG 12AWG Solar Extension Cable red+Black 4mm²/6mm² Voltage Class 1500V. Mounted Solar Plug Male and Female Connectors for Solar Panel Wire (6mm²-10AWG, 3Ft.) ($7.99 2/3/2025)

Part #2: Charge Controller To Battery

Solar Battery Cables 10 Gauge Power Inverter Cables with 3/8" Ring Terminals 10AWG Wire Tinned Copper Tray Extension Cable for Solar,RV,Auto Car,Boat (1M) ($11.98 2/3/2025)

Part #3: Inverter to Battery

Supplied with inverter

Figure 2: Two Solar Panels In Parallel Wiring Diagram $27.96

Figure 2, shown below, shows a wiring diagram of two solar panels connected in parallel. Figure 2, includes Part #1, #2, and #3 from Figure 1 and adds Part #4.

When solar panels are connected in parallel the current goes up so often used with a PWM solar charge controller that can handle the higher current.

The advantage of wiring the solar panels in parallel is you can use a cheap PWM solar charge controller.

Part #4: Solar Panel To Solar Panel In Parallel

BougeRV Solar Connectors Y Branch Parallel Adapter Cable Wire Plug Tool Kit for Solar Panel ($7.99 2/3/2025)

Figure 3: Two Solar Panels In Series Wiring Diagram $19.97

Figure 3, shown below, shows a wiring diagram of two solar panels connected in series. Figure 3, includes Part #1, #2, and #3 from Figure 1.

When solar panels are connected in series the voltage goes up so often used with a MPPT solar charge controller that can handle the higher voltages.

The advantage of wiring the solar panels in series is you can often wire the panels directly using the solar panel wires attached to the panels without using any extra wire.

Figure 4: Four Solar Panels In Series Parallel Wiring Diagram $27.96

Figure 4, shown below, shows a wiring diagram of four solar panels connected in series parallel. Figure 4, includes Part #1, #2, and #3 from Figure 1 and Part #4 from Figure 2.

Solar System Abbreviations

A: Amps
AC: Alternating current
Ah: Amp Hour
BMS: Battery Management System
DC: Direct current
I: Current
kWh: Kilowatt-hour
LiFePO4: Lithium Iron phosphate
MPPT: Maximum Power Point Tracking
PWM: Pulse Width Modulation
V: Volts
W: Watts
Wh: Watt hours

Solar System Formulas

Convert amp hours to watt hours: Wh = Ah × V. (Example: 1280 Wh = 100 Ah * 12.8V)
Convert watt hours to amp hours: Ah = Wh ÷ V. (Example: 100 Ah = 1280 Wh ÷ 12.8V)
Convert Watts Into Kilowatt-Hours: kWh = Wh ÷ 1,000. (Example: 1.28 kWh = 1280 Wh÷ 1,000)
Calculate Wh: Watts of device × Total hours used (Example: 7500 Wh = 750 W× 10 hours)
Convert Wh to kWh: kWh = Wh ÷ 1,000
Grid Electricity Total Cost: kWh used × your kWh rate.
W (Watts) =V (Voltage) × I (Current)
I (Current) = W (Watts) ÷ V (Voltage)

DIY Off-grid Solar System Guide

TOC

Solar System General

Solar System Savings

Solar System Design

Solar System Build

Solar System Appendix

Author

About the Author

Last Updated

Status

Disclaimer

General

Warning High Voltage

Overview

Off-grid vs Grid-tied

Off-grid solar system

Grid-tied solar system

What does off-grid mean?

Government Solar Subsidies

Cash vs Debt vs Lease Purchase

Ground vs Roof Installation

How to Connect Solar Electricity to House

Electricity Rates by State

Electricity Rates California

Highest Rates

California government policy

Grid Connection Fee

Income Based Fixed Rate Electricity Plan

Is Solar Worth it?

Solar Tariffs

kWh used by appliances

Cost to run appliances from grid

Examples

60 Watt incandescent light bulb for 1 hour ($0.0282)

1000 Watt space heater for 1 hour ($0.47)

Payback time

Refrigerator Payback

Standard Refrigerator Payback time

Mini Refrigerator Payback time

Low Energy Appliances

What loads are most practical to run on solar?

Low Energy Appliance Examples

Price per Watt vs Cost per kWh

Cost per kWh

100 Watt Solar System Cost per kWh

200 Watt Solar System Cost per kWh

Solar System

Solar Panels

What type of solar panel is best?

What is a shade tolerant solar panel

What is the difference between mono-facial & bifacial solar panels

How many kWh does my solar panel produce per day?

How many watts of solar panels do you need to charge your battery?

How long to charge my battery?

How many amps does a 100 watt panel produce?

Adding solar panels in series or parallel

Should I connect my solar panels in series or parallel?

What gauge wire should I use to connect the solar panel to the charge controller?

Why does a 12V solar panel have a voltage of around 17V?

What is Open Circuit Voltage (Voc)?

Does the Solar Panel Voc have to be less than the Maximum PV Input Voltage of the charge controller?

Charge controller

Should you get a PWM or MPPT charge controller?

What charge controller specifications do you need?

How many solar panels can I connect to my charge controller?

What is Maximum PV Input Voltage?

What is Maximum PV Input Power?

Battery

What type of battery chemistry is best?

What physical size of battery is best?

What terminal or lug size does my battery have?

What battery voltage should I use?

How powerful of a battery do I need?

What is the max watts or Max Discharge Current a battery can provide?

How to size the battery to the inverter?

Adding Batteries in Series or Parallel

How long can a space heater run on battery?

What size battery do you need to run an entire house?

Inverter