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Choosing A Water
Heater
If you are in a moderate
climate, consider a heat-pump water heater, which is more efficient
than an electric water heater. Though a heat-pump water heater may
have a high initial cost, it can save up to 50% of your
water-heating bill in moderate climates. Heat pumps can be added on
to your water heater or purchased as an integral part of a new water
heater.
The efficiency of water heaters is indicated by their energy factor
(EF), which 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 EFs ranging from 0.7
and 0.95; gas water heaters from 0.5 and 0.6, with some
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.
Everything else being equal, select a water heater with the highest
energy factor (EF). Also look for a water heater with at least
one-and-a-half inches of tank insulation and a heat trap.
In the United States, all water heaters are sold with EnergyGuide
labels to indicate their energy efficiency. These labels provide
estimated annual operating costs, and also indicate the cost of
operating the models with the highest annual operating cost and the
lowest annual operating cost. By comparing a model's annual
operating cost with the operating cost of the most efficient model,
you can compare their efficiencies.
Although some consumers buy water heaters based on the size of the
storage tank, the first-hour rating (FHR), provided on the
EnergyGuide label, is actually more important. The FHR is a measure
of how much hot water the heater will deliver during a busy hour.
Before you buy a water heater, estimate your household's peak-hour
hot water use (your water use during morning showers, for instance)
and look for a unit with an FHR in that range.
Demand water heaters are an option that should be considered when
replacing a water heater or when building a new home. Demand water
heaters only produce hot water when you need it, thereby avoiding
the energy losses due to storing hot water. However, they have a low
flow rate and may not be ideal for large families.
Tankless coil water heaters use a heating coil installed in the main
furnace for water heating. Common in oil-fired boilers and some
gas-fired boilers, tankless coil water heaters are an inefficient
means of heating water. A better solution is offered by indirect
water heaters, which use the main furnace to heat a fluid that is
then circulated through a tank of water. The energy stored by the
water tank allows the furnace to turn on and off less often, thereby
saving energy. If used with a high-efficiency boiler and a
well-insulated tank, this can be the least expensive means of
providing hot water.
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. Finally, it can save you energy and money to put some thought
into the best location for your water heater. Whenever possible, do
not install the water heater in an unheated basement. Also try to
minimize the piping runs to your bathroom and kitchen.
Copyright U.S.
Deptartment of Energy © 2004.
If you are interested in more, please
check out our
Annual Preventative Maintenance
Program
and you won't have to worry about at thing. |
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