Electric water heaters
A tall 80-gallon electric water heater is first wrapped with fiberglass insulation and then with construction foil to block radiant heat loss.
Heating domestic hot water is one of the greatest contributors to your monthly utility costs. For a typical family of four, an electric water heater can comprise 20 to 25 percent of their annual energy use. If you have an older model and don’t wish to replace it yet, there are ways to improve its efficiency.
Insulate electric water tank
Place the back of your hand against the water heater tank near the top or on the top. If it feels warm, it is losing heat. Adding an insulation wrap kit will save money. With a tall 80-gallon tank, the insulation wrap may not reach all the way to the floor. This is okay because the majority of the heat loss is from the upper part of the tank.
If you have some old fiberglass wall insulation, you can wrap that around the tank with the vapor barrier facing outside. Putting a layer of reflective radiant barrier over the insulation also helps. If you do that, it is important to tape and seal the joints in the insulation (where the insulation on the top meets the sides) to create an air-tight barrier.
Or you can buy a kit, which is roughly $20, easy to install and includes instructions (get one with an insulating value of at least R-10).
At least once a year, drain a gallon of water from the drain valve at the bottom of the tank. This will flush out sediment, which insulates the water from the heating element. Draining is more important with a gas or propane water heater, but it also helps some on an electric one.
Manage water temperature
It is important to keep the temperature as low as possible. A greater temperature difference between the hot water in the tank and the air in your basement or utility room increases tank standby losses. During the summer, these losses may heat up your house and make your air conditioner run longer, creating a double energy expense.
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 in much cold to tolerate it, it is too hot. I keep mine at 110 degrees. Most laundry detergents work well in cold water, and dishwashers have built in preheaters. Be sure to turn off electricity to the water heater before making any adjustments.
Feel the temperature of the water heater’s hot water outlet and cold-water inlet pipes. If they are fairly warm, it means hot water is naturally circulating upward and cooling off. Put tubular foam insulation on the water heater inlet and outlet water pipes to minimize that heat loss. Insulate the first two feet of the exposed piping.
If you are having other plumbing work done, consider having the plumber install heat trap fittings in the water heater to block this circulation. (It’s probably not cost-effective to pay a plumber just to come out for this.)
Installing a 240-volt timer can be effective if you typically do not use hot water during long and regular time periods and your family’s schedule fits accordingly.
New electric water heaters
If you are buying a new electric water heater, consider a 12-year warranty model. These have higher R-value foam insulation in the tank walls than a cheaper 6-year model. They also will have a higher EF (energy factor) rating. Look for an EF rating of .92 – .95 minimum. They may also have a vacation-mode setting to save electricity when you travel. Heat pump water heaters should also be strongly considered as they offer the lowest operating cost of all electric water heater types. They tend to cost more initially, and have special installation criteria, but heat pump water heaters can more than halve the cost of heating hot water for your home.