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CHOOSE ONCE... SAVE FOREVER!
The right water heater keeps on saving
... and saving... and saving!
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, tankless coil, indirect, and solar. It
is also possible to purchase water heaters that can be connected to your home's
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 EnergyGuide label required on storage water
heaters. EnergyGuide 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 flow rate.
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
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 reverse.
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 40 degree to 90 degree F (4.4
degrees to 32.2 degrees 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 frequently.
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 tankless 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 water heating.
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 water heater 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 and Certification Corporation (SRCC -- see Source List at the
end of this publication) provides a benchmark for comparing the performance of
some solar water heating systems.
The SRCC publishes performance ratings of both solar water-heating systems
and individual solar collectors. These published 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 projected
The Florida Solar Energy Center 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.
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 configurations. Some other considerations are
capacity, efficiency, and cost.
Although some consumers base their purchases on the size of the storage tank,
the peak hour demand capacity, referred to as the first-hour rating (FHR) on the
EnergyGuide 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 EnergyGuide 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 nonconventional
arrangements for combustion air intake and exhaust. These features, however, can
increase installation costs.
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 EnergyGuide 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 lifetime.
Units with longer warranties usually have higher price tags, though. Often,
the least expensive water heater to purchase is the most expensive to operate.
Our thanks to the U.S. Department of Energy
for use of this excerpted document
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