The least expensive water heaters to buy are the most expensive to operate."
Why Buy An Energy Efficient Water Heater?
Water heating is typically the third largest energy expense in your home (after space heating and cooling). It typically accounts for about 14% of your utility bill. If your gas water heater is more than 10 years old, it probably has an efficiency no higher than 50%. An old water heater can operate for years at very low efficiency before it finally fails. One way to reduce water heating costs would be to replace your old water heater with a new, higher-efficiency model.
About Water Heater Efficiency
A water heater's efficiency is measured by its energy factor (EF). EF is based on recovery efficiency, standby losses, and cycling losses. The higher the EF, the more efficient the water heater. Electric resistance water heaters have an EF ranging from 0.7 and 0.95; gas water heaters from 0.5 to 0.6, with a few high-efficiency models ranging around 0.8; oil water heaters from 0.7 and 0.85; and heat pump water heaters from 1.5 to 2.0.
Although many consumers make water heater purchase decisions based only on the size of the storage tank, the first-hour rating (FHR), provided on the Energy Guide label, is actually more important. The FHR is a measure of how much hot water the heater will deliver during a busy hour. The FHR is required by law to appear on the unit's Energy Guide label. Therefore, before you buy a water heater, estimate your household's peak-hour demand and look for a unit with an FHR in that range. And beware that a larger tank doesn't necessarily mean a higher FHR.
Tips for Buying a New Water Heater
- Choose a water heater with an appropriate first-hour rating (FHR) by estimating your family's peak-hour demand for hot water.
- Determine the appropriate fuel type for your water heater. If you are considering electricity, check with your local utility company for off-peak electricity rates for water heating. If available, this may be an attractive option to choose electric water heaters. Natural gas, oil and propane water heaters are less expensive to operate than electric models.
- If you are in a moderate climate (i.e., with relatively low heating loads), consider a Heat Pump Water Heater (HPWH), which is more efficient than a conventional electric water heater. Though a HPWH may have a high initial cost, it can save up to 50% of your water heating bill.
- For safety as well as energy-efficiency reasons, when buying gas- and oil-fired water heaters, look for units with sealed combustion or power venting to avoid back-drafting of combustion gases into the home.
- Everything else being equal, select a water heater with the highest energy factor (EF). However, you should note that the EF of one type of heater is not comparable to another type. For example, an electric water heater with an EF of 0.9 may cost more to operate than a gas water heater with an EF of 0.7.
- Whenever possible, do not install the water heater in an unheated basement. Also try to minimize the length of piping runs to your bathroom and kitchen.
Tips for Lowering Your Water Heater's Energy Usage
- Install aerators in faucets and low-flow shower heads that may reduce your hot water consumption by half.
- Repair leaky faucets and shower heads. A leak of one drip per second can cost $1 per month.
- Insulate your hot water storage tank and pipes, but be careful not to cover the tank thermostat(s).
- Lower the thermostat(s) on your water heater to 120°F. Electric water heaters often have two thermostats-one each for the upper and lower heating elements. These should be adjusted to the same level to prevent one element from doing all the work and wearing out prematurely.
- For electric water heaters, install a timer that can automatically turn the hot water off at night and on in the morning. A simple timer can pay for itself in less than a year.
- Install a heat trap above the water heater. A heat trap is a simple check valve or piping arrangement that prevents "thermosyphoning"-the tendency of hot water to rise up from the tank into the pipes-thereby lowering standby losses.
- Drain a quart of water from your hot water tank every 3 months to remove sediment that prevents heat transfer and lowers the unit's efficiency.
- Take more showers than baths. Baths use the most hot water in an average household. You use 15 to 25 gallons of hot water for a bath and less than 10 gallons for a 5-minute shower.
What's New: Water Heaters
Point-of-use water heaters:
Point-of-use water heaters are also known as "tankless" heaters because they have no (or only a tiny) storage tank. They are relatively small units that provide hot water on demand. They use gas or electricity for fuel, and can be installed near demand points, such as under kitchen sinks. They are often more expensive than a conventional water heater, but can cost less to operate since they don't maintain a tankfull of hot water when not in use. A tankless heater typically provides 1-2 gallons of hot water per minute. Before installing a tankless water heater in your home, make sure its reduced capacity will be adequate for your needs.
Solar water heaters:
A solar water heater typically includes collectors mounted on the roof or in a clear area of the yard, a separate storage tank near the conventional heater in the home, connecting pipe, and a controller. Solar water heaters can reduce the annual fuel cost of supplying hot water to your home by more than half. Throughout the year, the solar system preheats the water before it reaches the conventional water heater. During the summer, it may provide all the required heat.
A desuperheater is an attachment to your air conditioner or heat pump that allows waste heat from that device to help heat domestic water. In hot climates, a desuperheater can provide most of a home's hot water needs during the summer.
Updated July 11, 2001