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The chart to the left shows our bills for the past couple of years, with heating-degree-days and cooling-degree-days overlaid. Note that we used less power in summer and fall of 2018--after our geothermal system was installed--than in the previous summer and fall. We used about twice as much power in the recent colder months, however, compared to the same period in the previous year.
April 2024
The system is still plugging along reliably after nearly 6 years. Annual maintenance costs are rising, but what isn't? This year, I paid $604 for the annual maintenance, which included checking the refrigerant levels, the heating and cooling modes, the group loop water levels, replacing the humidifier electrolysis tank, replacing the 1-year filter, cleaning and sanitizing the condensation drains, and some other stuff. Last year, the same service cost $381.
August 2021
After analyzing electric power usage for September 2020 through July 2021, I estimated that the heat pump used a total of about 2,400 KWhr of electricity. At local rates that amounts to a little over $200 per year total for heating and cooling. Not bad! That's about 20% of our household electricity consumption (not including EV charging).
System maintenance is low--changing the air filter once per year and replacing the ultra-violet air stream sanitizer--although that's over $100/year if I do it myself. More if I bring in a tech.
March 2020
After nearly two years with our geothermal system, it looks like our propane usage has decreased by about 81%. Our propane usage amounts to about 97 gallons per year (compared to about 503 gallons per year prior to installation). At present propane prices (about $3.40/gallon) that's about $1380/year savings in propane.
Naturally our electric usage has increased, but we recently subscribed to a Community Solar Installation to make up the difference between what our solar arrays produce and what we need.
We still use propane for drying laundry, and for water heating. Our geothermal system dumps waste heat into a water tank to preheat water going into the propane water heater, bring the ground water up to about 85 degrees. In addition, my solar thermal system boosts the temperature of that water further--to about 115 degree on a sunny day.
If I eventually replace the propane water heater with a tankless heater, we could further reduce our net carbon emissions.
February 2019
The geothermal system seems to be driving up our winter electricity usage. Our usage for Mid- November through mid-January has been about 985 KWhr/month--about $85/month.
While I am very pleased with the geothermal system performance over most of the year, the high electric usage in the coldest months of winter come when our solar power production is at its lowest. That means that even if we offset our average annual usage with solar power through net metering, we will be relying on credit from that net metering and (therefore) on fossil-fuel-produced power in the winter more than I would prefer.
On the other hand, we have substantially reduced our propane usage after getting rid of the old furnace.
August 2018
Since we installed the geothermal heating and cooling system in summer 2018, our summer electricity usage appears to be lower. I say “appears to be” because our electric bills have been a mess; 6 of the past 13 monthly bills were estimates, with corrections applied during months the meter was actually read. In addition, my retirement a little over a year ago means that my electric car is using less electric power. Nevertheless, I think I can say the following:
Last year, we were paying $35-$53 for summertime power owing to air conditioning (A/C) costs, and maybe an A/C system that was getting old.
This summer, we are only paying $12-$15 dollars most months (mostly connection charges and meter reading fees) for power. That’s about 1/3 the peak use in August last year. We also are producing more power than we need monthly, giving us credit against future electric bills.
24 July 2018
In June 2018, we had a geothermal system installed to heat and cool our home. We hoped to reduce our reliance on propane for heating, and we were pretty sure that our air conditioner needed replacing anyway. Geothermal seemed like the least carbon-intensive solution for operations.
Some statistics:
Size: 4-tons
Type: Four vertical wells (as opposed to horizontal wells or lake coils)
Cost: $16,921 (after 30% income tax deduction from Federal government over the next couple of years; original price: $24,173)
The cost was a little higher than it might have been; we sprung extra $ for upgraded air filtration and built-in humidifier, as well as a deluxe 80-gallon water tank with stainless steel heating coil to use as a preheater for hot water. Waste heat from the heat pump in the summer heats the tank to about 75 degrees. I plan to plumb my solar water heater into this tank using the stainless steel heating coil for additional preheating of the water.
As of July 2018, it's too soon to say how this will affect our electric bills or our propane bills.
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