Chapter 11: Making Your Water Heater Efficient


Hot water heating comprises approximately 20% of a household’s energy consumption.  There are many avenues to savings: using less hot water, increasing the efficiency of an existing system and considering the purchase of a more efficient system.

Overview of Efficient Hot Water Heating & Purchasing Considerations

This resource from the American Council for an Energy-Efficient Economy (ACEEE) contains comparison information on the different types of hot water heaters (tankless/on-demand, solar, heat pump).

Lower Your Water Heater Temperature

You can reduce your water heating costs by simply lowering the thermostat setting on your water heater. For each 10ºF reduction in water temperature, you can save between 3%–5% in energy costs.  Although some manufacturers set water heater thermostats at 140ºF, most households usually only require them set at 120ºF. Water heated at 140ºF also poses a safety hazard—scalding.  See this document for more information.

Insulate Your Water Heater

Unless your water heater's storage tank already has a high R-value of insulation (at least R-24), adding insulation to it can reduce standby heat losses by 25%–45%. This will save you around 4%–9% in water heating costs.  If you don't know your water heater tank's R-value, touch it. A tank that's warm to the touch needs additional insulation.

Insulating your storage water heater tank is fairly simple and inexpensive, and it will pay for itself in about a year. You can find pre-cut jackets or blankets available from around $10–$20. Choose one with an insulating value of at least R-8. Some utilities sell them at low prices, offer rebates, and even install them at a low or no cost.  Read more about insulating your water heater.

A Special Note on Insulating Gas Water Heaters

The installation of insulating blankets or jackets on gas and oil-fired water heater tanks is more difficult than those for electric water heater tanks. It's best to have a qualified plumbing and heating contractor add the insulation. If you want to install it yourself, read and follow the directions very carefully. Keep the jacket or blanket away from the drain at the bottom and the flue at the top. Make sure the airflow to the burner isn't obstructed. Leave the thermostat uncovered, and don't insulate the top of a gas water heater tank—the insulation is combustible and can interfere with the draft diverter.  More information is available at this link.

Insulate Hot Water Pipes

A useful guide for insulating hot water pipes is available here.

Solar Water Heating

Solar works in Kentucky!  “Solar water heaters have been in use for more than a century and today there are tens of millions of units in use around the world. While solar water heating is not very common in the United States, it's popularity is growing. The technology is in widespread use in other countries such as Israel, China, and Germany, and in recent years the market has begun to grow in the United States. Many people mistakenly think that solar water heating can't work in Kentucky because of our climate. In reality, Kentucky's solar energy resources are quite good and enable us to heat 50 - 80% of a home's annual hot water needs with solar energy.” (From Kentucky Solar Partnership webpage).

Frankfort is home to the Kentucky Solar Partnership (KSP).  The KSP website has information on solar water heating in Kentucky.  You can contact KSP Director Andy McDonald at 502-227-4562.