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Gas Water Heater Efficiency
WATER
HEATER EFFICIENCY
The energy
efficiency of a storage water heater is indicated by its energy factor
(EF), an overall efficiency based on the use of 64 gallons of hot
water per day. The first national appliance efficiency standards for
water heaters took effect in 1990. New standards, which took effect in
January 2004, increased the minimum efficiency levels of water
heaters.
The most efficient gas-fired storage water heaters have energy
factors ranging from 0.60 to 0.65, corresponding to estimated gas use
below 250 therms/year. Condensing water heaters have energy factors as
high as 0.86.
With demand
water heaters, the manufacturers provide different specifications:
the energy input (Btu/hour for gas, kilowatts [kW] for electric); the
temperature rise achievable at the rated flow; the flow rate at the
listed temperature rise; and so on. In comparing different models, be
aware that you aren’t always looking at direct comparisons, especially
with temperature rise and flow rate. For example, while one model
might list the flow rate at a 100°F temperature rise, another might
list the flow rate at 70°. Until there are industry-standard ratings
for temperature rise and flow rates, it will be difficult to compare
the performance of products from different companies. Some companies
are beginning to publish energy factor ratings for these products and
this information should make for easier comparisons.
COMPARING
THE TRUE COSTS OF WATER HEATERS
When comparing the cost of various water heating options, keep in mind
that there are two types of cost you need to look at: purchase cost
and operating cost. Life-cycle costs, which take into account both the
initial costs and operating costs of different water heaters, provide
a much more accurate representation of the true costs of the water
heater than the purchase price alone. Life-cycle costs for the most
common types of water heaters under typical operating conditions are
shown in the table
here. When both purchase and operating costs are taken into
account, one of the least expensive systems to buy (conventional
electric storage) is one of the most costly to operate over a 13-year
period. An electric heat pump water heater, though expensive to
purchase, has a much lower cost over the long term.
UPGRADING
YOUR EXISTING WATER HEATER
Even if you
aren’t going to buy a new water heater, you can save a lot of energy
and money with your existing system by following a few simple
suggestions.
 | Conserve
Water: Your biggest opportunity for savings is to use less hot
water. In addition to saving energy (and money), cutting down on hot
water use helps conserve dwindling water supplies, which in some
parts of the country is a critical problem. A family of four each
showering five minutes a day can use about 700 gallons per week—a
three-year drinking water supply for one person! Water-conserving
showerheads and faucet aerators can cut hot water use in half. That
family of four can save 14,000 gallons of water a year and the
energy required to heat it. |
| Insulate
Your Existing Water Heater: Installing an insulating jacket on your
existing water heater is one of the most effective do-it-yourself
energy-saving projects, especially if your water heater is in an
unheated basement or space. The insulating jacket will reduce
standby heat loss—heat lost through the walls of the tank—by 25–40%,
saving 4–9% on your water heating bills. Water heater insulation
jackets are widely available for around $10. Some newer water
heaters come with fairly high insulation levels, reducing (though
not eliminating) the economic advantages of adding additional
insulation. In fact, some manufacturers recommend against installing
insulating jackets on their energy-efficient models. Always follow
directions carefully when installing an insulation jacket. Leave the
thermostat(s) accessible. With conventional gas- and oil-fired water
heaters, you need to be careful not to restrict the air inlet(s) at
the bottom or the draft hood at the top. |
| Insulate Hot
Water Pipes: Insulating your hot water pipes will reduce losses as
the hot water is flowing to your faucet and, more importantly, it
will reduce standby losses when the tap is turned off and then back
on within an hour or so. A great deal of energy and water is wasted
waiting for the hot water to reach the tap. Even when pipes are
insulated, the water in the pipes will eventually cool, but it stays
warmer much longer than it would if the pipes weren’t insulated. |
| Lower the
Water Heater Temperature: Keep your water heater thermostat set at
the lowest temperature that provides you with sufficient hot water.
For most households, 120°F water is fine (about midway between the
“low” and “medium” setting). Each 10°F reduction in water
temperature will generally save 3–5% on your water heating costs.
When you are going away on vacation, you can turn the thermostat
down to the lowest possible setting, or turn the water heater off
altogether for additional savings. With a gas water heater, make
sure you know how to relight the pilot if you’re going to turn it
off while away |
Here is more information on water heater efficiency!
Water Heater
Circulation Pump
Gas Water Heater Efficiency |
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Water Heater Efficiency