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Tubular foam insulation placed over water pipes immediately above the water heater helps minimize energy-robbing currents.
Photo by James Dulley
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This tall, 80-gallon electric water heater is first wrapped with fiberglass insulation and then with construction foil to block radiant heat loss.
Photo by James Dulley
Question:My 80-gallon electric water heater is getting old, but it doesn’t leak. Are there things I can do to help it operate more efficiently?
Answer: An electric water heater is a simple device. It is basically a big, insulated tank of water with an upper and a lower resistance-heating element. The lower element heats cold water that enters the bottom of the tank; the upper one comes on to ensure a heated supply of water at the top of the tank, where hot water is released.
Even when you do not use any hot water, the lower element will cycle on at times to make up the heat lost through the tank walls. This standby loss can be significant, as most older units have a very thin layer of fiberglass insulation between the glass-lined metal tank and its external skin.
Place a hand against the water heater tank, near or on the top. If it feels warm, it is losing heat and is therefore a good candidate for an insulation wrap kit. Available from home improvement stores for about $20, these kits are easy to install. Get one with an insulating value of at least R-10. It’s okay if the insulation wrap doesn’t reach all the way to the bottom of the tank, because most heat loss comes from the upper part of the tank.
You can make your own tank wrap from rolls of fiberglass wall insulation—just be sure to wear gloves, a breathing mask and appropriate eye protection. Wrap the rolls around the tank, with the vapor barrier facing to the outside. A layer of reflective radiant barrier over the insulation also helps stop heat loss. Tape and seal the joints where the insulation on top meets the sides to create an airtight barrier.
Heat can also be lost through the tank’s piping. Feel the temperature of the hot-water outlet pipes. If they are fairly warm, it means hot water is circulating upward and cooling off. This is another form of standby loss that you can combat by installing tubular foam insulation on the first 4 to 6 inches of the exposed pipes. Available at home improvement stores, this type of insulation is split on one side, making it easy to install over the pipes.
Draining the tank at least once a year helps improve efficiency. Drain a gallon of water from the drain valve at the bottom of the tank to flush out sediment that collects there, insulating water from the heating element. This is more important to do with a gas water heater, but it also helps some on an electric one.
Adjusting the water temperature is another way to improve efficiency—just be sure to turn off electricity to the water heater before changing any settings.
Check the temperature of the hot water at a faucet where you use the most hot water. If you keep it so hot that you have to mix much cold with it to tolerate the temperature, it is too hot. Most experts recommend a setting of 115 to 120 degrees F, but you may be able to get away with a lower setting. I keep my water heater set at 110 F.
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