Selecting a New Water Heater
Many homeowners wait until their water heater fails
before shopping for a replacement. Because they are in a hurry to regain their hot water
supply, they are often unable to take the time to shop for the most energy-efficient unit
for their specific needs. This is unfortunate, because the cost of purchasing and
operating a water heater can vary greatly, depending on the type, brand, and model
selected and on the quality of the installation.
To avoid this scenario, you might want to do
some research now-before you are faced with an emergency purchase. Familiarize yourself
today with the options that will allow you to make an informed decision when the need to
buy a new water heater arises.
Types of Water Heaters Available
Within the last few years, a variety of water heaters have become available to consumers.
The following types of water heaters are now on the market: conventional storage, demand,
heat pump, tank-less coil, indirect, and solar. It is also possible to purchase water
heaters that can be connected to your home's space-heating system.
Storage Water Heaters
A variety of fuel options are available for conventional storage water
heaters-electricity, natural gas, oil, and propane. Ranging in size from 20 to 80 gallons
(75.7 to 302.8 liters), storage water heaters remain the most popular type for residential
heating needs in the United States. A storage heater operates by releasing hot water from
the top of the tank when the hot water tap is turned on. To replace that hot water, cold
water enters the bottom of the tank, ensuring that the tank is always full.
Because the water is constantly heated in the
tank, energy can be wasted even when no faucet is on. This is called standby heat loss.
Newer, more energy-efficient storage models can significantly reduce the amount of standby
heat loss, making them much less expensive to operate. To determine the most
energy-efficient model, consult the Energy Guide label required on storage water heaters.
Energy Guide labels indicate either the annual estimated cost of operating the system or
energy efficiency ratings.
Demand Water Heaters
It is possible to completely eliminate standby heat losses from the tank and reduce energy
consumption 20% to 30% with demand (or instantaneous) water heaters, which do not have
storage tanks. Cold water travels through a pipe into the unit, and either a gas burner or
an electric element heats the water only when needed. With these systems, you never run
out of hot water. But there is one potential drawback with demand water heaters- limited
Typically, demand heaters provide hot water at a
rate of 2 to 4 gallons (7.6 to 15.2 liters) per minute. This flow rate might suffice if
your household does not use hot water at more than one location at the same time (e.g.,
showering and doing laundry simultaneously). To meet hot water demand when multiple
faucets are being used, demand heaters can be installed in parallel sequence. Although
gas-fired demand heaters tend to have higher flow rates than electric ones, they can waste
energy even when no water is being heated if their pilot lights stay on. However, the
amount of energy consumed by a pilot light is quite small.
Heat Pump Water Heaters Heat pump water heaters
use electricity to move heat from one place to another instead of generating heat
directly. To heat water for homes, heat pump water heaters work like refrigerators in
Heat pump water heaters can be purchased as
integral units with built-in water storage tanks or as add-ons that can be retrofitted to
an existing water-heater tank. These systems have a high initial cost. They also require
installation in locations that remain in the 40ø to 90ø F (4.4ø to 32.2ø C) range
year-round and contain at least 1000 cubic feet (28.3 cubic meters) of air space around
the water heaters. To operate most efficiently, they should be placed in areas having
excess heat, such as furnace rooms. They will not work well in a cold space.
Tankless Coil and Indirect Water Heaters
A home's space-heating system can also be used to heat water. Two types of water heaters
that use this system are tankless coil and indirect. No separate storage tank is needed in
the tankless coil water heater because water is heated directly inside the boiler in a
hydronic (i.e., hot water) heating system. The water flows through a heat exchanger in the
boiler whenever a hot water faucet is turned on. During colder months, the tankless coil
works well because the heating system is used regularly. However, the system is less
efficient during warmer months and in warmer climates when the boiler is used less
A separate storage tank is required with an
indirect water heater. Like the tankless coil, the indirect water heater circulates water
through a heat exchanger in the boiler. But this heated water then flows to an insulated
storage tank. Because the boiler does not need to operate frequently, this system is more
efficient than the tank-less coil. In fact, when an indirect water heater is used with a
highly efficient boiler, the combination may provide one of the least expensive methods of
Solar Water Heaters
Through specially designed systems, energy from the sun can be used to heat water for your
home. Depending on climate and water use, a properly designed, installed, and maintained
solar water heater can meet from half to nearly all of a home's hot water demand.
Two features, a collector and a storage tank,
characterize most solar water heaters. Beyond these common features, solar water-heating
systems can vary significantly in design. The various system designs can be classified as
passive or active and as direct (also called open loop) or indirect (also called closed
Passive systems operate without pumps and
controls and can be more reliable, more durable, easier to maintain, longer lasting, and
less expensive to operate than active systems. Active solar water heaters incorporate
pumps and controls to move heat-transfer fluids from the collectors to the storage tanks.
Both active and passive solar water-heating
systems often require "conventional" water heaters as backups, or the solar
systems function as preheaters for the conventional units.
A direct solar water-heating system circulates
household water through collectors and is not appropriate in climates in which freezing
temperatures occur. An indirect system should not experience problems with freezing
because the fluid in the collectors is usually a form of antifreeze.
If you are considering purchasing a solar
water-heating system, you may want to compare products from different manufacturers. The
Solar Rating & Certification Corporation (SRCC-see Source List at the end of this
publication) provides a bench-mark for comparing the performance of some solar water
The SRCC publishes performance ratings of both
solar water-heating systems and individual solar collectors. These pubbished ratings are
the results of independent, third-party laboratory testing of these products. All systems
and collectors that have been certified by the SRCC will bear the SRCC label.
Keep in mind, though, that simply having an SRCC
label does not imply that the product has a superior performance. Carefully compare SRCC
label information on different brands and models to ensure that you are fully aware of
The Florida Solar Energy Center (FSEC- see
Source List) also provides information on solar manufacturers and contractors. It also
maintains solar equipment testing facilities and publishes performance ratings for solar
water heating systems.
Just choosing a solar water heater with good
ratings is not enough, though. Proper design, sizing, installation, and maintenance are
also critical to ensure efficient system performance.
Although the purchase and installation prices of
solar water heaters are usually higher than those of conventional types, operating costs
are much lower.
For more information about solar water-heating
systems, contact the Energy Efficiency and Renewable Energy Clearinghouse (EREC-see Source
Criteria for Selection
As with any purchase, balance the pros and cons of the different water heaters in light of
your particular needs. There are numerous factors to consider when choosing a new water
heater. This publication has already described different system con-figurations. Some
other considerations are capacity, efficiency, and cost.
Although some consumers base their purchase on the size of the storage tank, the
peak hour demand capacity, referred to as the first-hour rating (FHR) on the Energy Guide
label, is actually the more important figure. The FHR is a measure of how much hot water
the heater will deliver during a busy hour, and it is required by law to appear on the
unit's Energy Guide label. Therefore, before you shop, estimate your household's peak hour
demand and look for a unit with an FHR in that range.
Gas water heaters have higher FHRs than electric
water heaters of the same storage capacity. Therefore, it may be possible to meet your
water-heating needs with a gas unit that has a smaller storage tank than an electric unit
with the same FHR. More efficient gas water heaters use various non-conventional
arrangements for combustion air intake and exhaust. These features, however, can increase
Once you have decided what type of water heater best suits your needs, determine which
water heater in that category is the most fuel efficient. The best indicator of a heater's
efficiency is its Energy Factor (EF), which is based on recovery efficiency (i.e., how
efficiently the heat from the energy source is transferred to the water), standby losses
(i.e., the percentage of heat lost per hour from the stored water compared to the heat
content of the water), and cycling losses.
The higher the EF, the more efficient the water
heater. Electric resistance water heaters have an EF between 0.7 and 0.95; gas heaters
have an EF between 0.5 and 0.6, with some high-efficiency models around 0.8; oil heaters
range from 0.7 to 0.85; and heat pump water heaters range from 1.5 to 2.0. Product
literature from manufacturers usually gives the appliance's EF rating. If it does not, you
can obtain it by contacting an appliance manufacturer association (see Source List).
Some other energy efficiency features to look
for are tanks with at least 1.5 inches (3.8 centimeters) of foam insulation and energy
efficiency ratings shown on the Energy Guide labels.
Another factor uppermost in many consumers' minds is cost, which encompasses purchase
price and lifetime maintenance and operation expenses.
When choosing among different models, it is wise
to analyze the life-cycle cost-the total of all costs and benefits associated with a
purchase during its estimated life-time. More information on conducting life-cycle cost
analyses is available from EREC.
Units with longer warranties usually have higher
price tags, though. Often, the least expensive water heater to purchase is the most
expensive to operate.
The following organizations and publications
provide more information on hot water energy efficiency. Much of the information included
in this publication was obtained from several of these sources. This list does not cover
all the available books, reports, and articles on hot water energy efficiency, nor is the
mention of any publication to be considered a recommendation or endorsement. To obtain the
publications in this list, contact your local library or bookstore or the publisher. Check
publication prices through your bookstore or the publisher before placing an order.
American Council for an Energy-Efficient Economy
(ACEEE) 1001 Connecticut Avenue, NW, Suite 801 Washington, DC 20036 (202) 429-8873 or 2140
Shattuck Avenue, Suite 202 Berkeley, CA 94704
ACEEE provides general and technical information
on energy efficiency, including these publications: The Consumer Guide to Home Energy
Savings, The Most Energy-Efficient Appliances, and Saving Energy and Money with Home
Appliances. These publications can be ordered by writing the ACEEE office in Berkeley,
Association of Home Appliance Manufacturers
(AHAM) Information Center 20 North Wacker Drive Chicago, IL 60606 (312) 984-5800 ext. 315
AHAM provides energy efficiency information for
specific brands of major appliances. The association also runs a certification program for
certain types of appliances.
Florida Solar Energy Center (FSEC) Attn: Public
Information Office 300 State Road 401 Cape Canaveral, FL 32920 (407) 783-0300
FSEC is a state-supported solar research
facility that answers questions on solar and other forms of renewable energy. FSEC
provides free information and publications, including a quarterly newsletter, to the
Gas Appliance Manufacturers Association, Inc.
(GAMA) 1901 North Moore Street, Suite 1100 Arlington, VA 22209 (703) 525-9565
GAMAhas information on residential gas
appliances and equipment, electric and oil-fired water heaters, and oil-fired warm air
Solar Rating & Certification Corporation
(SRCC) 122 C Street, NW, 4th Floor Washington, DC 20001 (202) 383-2570
SRCC is an independent, nonprofit organization
that certifies and rates the performance of solar equipment and systems. Further
information about energy-efficient water heating can be obtained by contacting: The Energy
Efficiency and Renewable Energy Clearinghouse (EREC) P.O. Box 3048 Merrifield, VA 22116
EREC provides free general and technical
information to the public on a wide spectrum of topics and technologies pertaining to
energy efficiency and renewable energy. Also contact your state and local government
energy offices as well as your utility for additional information on energy-efficient
water heaters, installation, and rebate or incentive programs.