The next time you pay your utility bill, try

one simple calculation. Divide the total

amount by seven. The result is the amount

you spend to heat your water. (If you

receive separate utility bills for gas and

electricity, use the gas bill for this calculation if you have a gas water heater; use 

the electric bill if you have an electric

water heater.)

Of course, you may think this cost is a

small price to pay for the convenience of 

a hot shower. But during the course of a

year, this cost adds up. And when you

consider that 95 million households in this

country pay the same percentage, it is easy

to see how much money—and energy—is

used to heat water.

Several measures can help you decrease

water-heating costs in your home. Some

specific actions include reducing the

amount of hot water used, making your

water-heating system more energy

efficient, and using off-peak power to 

heat water. 

Reducing the Amount of 

Hot Water Used

Generally, four destination points in the

home are recognized as end uses for hot

water: faucets, showers, dishwashers, and

washing machines. Now, you do not have

to take cold showers, dine on dirty dishes,

or wear dirty clothes to reduce your hotwater consumption. Less radical measures

are available that will be virtually unnoticeable once you apply them.

Faucets and Showers 

Simply repairing leaks in faucets and

showers can save hot water. A leak of one

drip per second can cost $1 per month, yet

could be repaired in a few minutes for less

than that. And some apparently insignificant steps, when practiced routinely at

your household, could have significant

results. For example, turning the hot-water

faucet off while shaving or brushing your

teeth, as opposed to letting the water run,

can also reduce water-heating costs.

Another option is limiting the amount 

of time you spend in the shower.

Other actions may require a small investment of time and money. Installing lowflow showerheads and faucet aerators can

save significant amounts of hot water.

Low-flow showerheads can reduce hotwater consumption for bathing by 30%, yet

still provide a strong, invigorating spray.

Faucet aerators, when applied in commercial and multifamily buildings where

water is constantly circulated, can also

reduce water-heating energy consumption.

Older showerheads deliver 4 to 5 gallons

(15.1 to 18.9 liters) of water per minute.

However, the Energy Policy Act of 1992 

Energy-Efficient 

CLEARINGHOUSE

Water Heating

ENERGY

EFFICIENCY AND

RENEWABLE

ENERGY

T OF ENERGY

DEPARTMEN

U

E

NITED STAT S OF A

ERICA

M

vc-cd14-a1242-01

Although a low-flow showerhead (bottom)

delivers slightly less water than a standard

showerhead (top), the spray can still be 

invigorating.

This document was produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a DOE national laboratory.

The document was produced by the Technical Information Program, under the DOE Office of Energy Efficiency and Renewable Energy. The Energy Efficiency

and Renewable Energy Clearinghouse (EREC) is operated by NCI Information Systems, Inc., for NREL/DOE. The statements contained herein are based on

information known to EREC and NREL at the time of printing. No recommendation or endorsement of any product or service is implied if mentioned by EREC.

Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 10% postconsumer waste

DOE/GO-10095-063

FS 204

January 1995
sets maximum water flow rates at 

2.5 gallons (9.5 liters) per minute at a 

standard residential water pressure of 

80 pounds per square inch (552 kilopascals).

A quick test can help you determine if

your shower is a good candidate for a

showerhead replacement. Turn on the

shower to the normal pressure you use,

hold a bucket that has been marked in gallon increments under the spray, and time

how many seconds it takes to fill the

bucket to the 1-gallon (3.8-liter) mark. If it

takes less than 20 seconds, you could benefit from a low-flow showerhead. A topquality, low-flow showerhead will cost $10

to $20 and pay for itself in energy saved

within 4 months. Lower quality showerheads may simply restrict water flow,

which often results in poor performance.

Because of the different uses of bathroom

and kitchen faucets, you may need to have

different water flow rates in each location.

For bathroom faucets, aerators that deliver

0.5 to 1 gallon (1.9 to 3.8 liters) of water

per minute may be sufficient. Kitchen

faucets may require a higher flow rate of 

2 to 4 gallons (7.6 to 15.1 liters) per minute

if you regularly fill the sink for washing

dishes. On the other hand, if you tend to

let the water run when washing dishes,

the lower flow rate of 0.5 to 1 gallon per

minute may be more appropriate. Some

aerators come with shut-off valves that

allow you to stop the flow of water without affecting the temperature.

Automatic Dishwashers

A relatively common assumption is that

washing dishes by hand saves hot water.

However, washing dishes by hand several

times a day could be more expensive than

operating some automatic dishwashers. If

properly used, an efficient dishwasher can

consume less energy than washing dishes

by hand, particularly when you only operate the dishwasher with full loads.

The biggest cost of operating a dishwasher

comes from the energy required to heat

the water before it ever makes it to the

machine. Heating water for an automatic

dishwasher can represent about 80% of

the energy required to run this appliance.

Average dishwashers use 8 to 14 gallons

(30.3 to 53 liters) of water for a complete

wash cycle and require a water temperature of 140°F (60°C) for optimum cleaning.

But setting your water heater so high

could result in excessive standby heat loss.

This type of heat loss occurs because water

is constantly heated in the storage tank,

even when no hot water is used. Furthermore, a water heater temperature of 120°F

(48.9°C) is sufficient for other uses of hot

water in the home. The question, then, is

must you give up effective cleaning for hotwater energy savings? The answer is no.

A “booster” heater can increase the temperature of the water entering the dishwasher to the 140°F recommended for

cleaning. Some dishwashers have built-in

boosters that will automatically raise the

water temperature, while others require

manual selection before the wash cycle

begins. A booster heater can add about 

$30 to the cost of a new dishwasher but

should pay for itself in water-heating

energy savings in about 1 year if you also

lower your water heater temperature.

Reducing the water heater temperature 

is not advisable, however, if your dishwasher does not have a booster heater.

Another feature that reduces hot-water

use in dishwashers is the availability of

cycle selections. Shorter cycles require less

water, thereby reducing the energy cost.

The most efficient dishwasher currently

on the market can cost half as much to

operate as the most inefficient model. If

you are planning to purchase a new dishwasher, check the EnergyGuide labels and

compare the approximate yearly energy

costs among brands. Dishwashers fall into

one of two categories—compact capacity

or standard capacity. Although compactcapacity dishwashers may appear to be

more energy efficient, they hold fewer

dishes and may force you to use the appliance more frequently than you would use

a standard-capacity model. In this case,

your energy costs could be higher than

with the standard-capacity dishwasher.

2

Turning the hot-water

faucet off while 

shaving or brushing

your teeth, as opposed

to letting the water

run, can reduce

water-heating costs. 

An efficient automatic

dishwasher can 

consume less energy

than washing dishes

by hand, particularly

when you only 

operate the dishwasher

with full loads.
Washing Machines

Like dishwashers, much of the cost—up to

90%—of operating washing machines is

associated with the energy needed to heat

the water. Unlike dishwashers, washing

machines do not require a minimum 

temperature for optimum cleaning. Either

cold or warm water can be used for washing most laundry loads; cold water is

always sufficient for rinsing. Make sure

you follow the cold-water washing

instructions for your particular laundry

detergent. Washing only full loads is

another good rule of thumb for reducing

hot-water consumption in clothes washers.

As you would for dishwashers, consult

the EnergyGuide labels when shopping

for a new washing machine. Inefficient

washing machines can cost three times as

much to operate as efficient machines.

Select a machine that allows you to adjust

the water temperature and water levels for

the size of the load. Also, front-loading

machines use less water and, consequently, less energy than top loaders.

However, in this country, front loaders are

not as widely available as top loaders.

Keep in mind that the capacity of front

loaders may be smaller than that of most

top-loading machines. 

Smaller capacity washing machines often

have better EnergyGuide ratings. However, a reduced capacity might cause you

to increase the number of loads you wash

and possibly increase your energy costs.

Faucets, showerheads, dishwashers, and

washing machines are only destination

points for hot water in your home. The

journey of your hot water before it reaches

these outlets can be fraught with opportunities for energy losses. Fortunately, you

can reduce the incidence of water heat loss

from the point of departure to the point of

arrival by applying a few basic measures.

Increasing Water-Heating 

System Efficiency

Reducing hot-water usage is primarily a

matter of common sense and exerting a little extra effort to not be wasteful. Once you

have applied a few simple, low-cost measures for reducing hot-water consumption,

you may want to consider water-heating

system improvements if you wish to further reduce your energy bill.

Lower Your Water Heater Thermostat

One simple step for reducing waterheating energy costs is lowering the thermostat setting on your water heater.

Although some manufacturers set water

heaters at 140°F (60°C), 120°F (48.9°C) is

satisfactory for most household needs.

Furthermore, when heated to 140°F, water

can pose a safety hazard (i.e., scalding).

For each 10°F (5.6°C) reduction in water

temperature, water-heating energy consumption can be reduced 3% to 5%.

If your dishwasher does not have a booster

heater, lowering the water-heating temperature is not recommended. Also, many

dishwasher detergents are formulated to

clean effectively at 140°F and may not perform adequately at lower temperatures.

(See previous discussion on Automatic 

Dishwashers.)

On gas water heaters, thermostats are usually visible. Electric water heaters, on the

other hand, may have thermostats positioned behind screw-on plates. As a safety

precaution, shut off electric current to the

water heater before removing the plates.

Keep in mind that electric water heaters

may have two thermostats to adjust—one

each for the upper and lower heating elements—and adjusting these is tricky. Talk

to your local water-heating professional

for help with this.

When you plan to be away from home for

an extended period of time (at least 3 days),

turning the water heater thermostat down

to the lowest setting, or even turning the

heater off completely, can help you achieve

additional savings. Be sure you know how

to relight the pilot light on your gas heater,

though, before you turn it off.

3

Unlike dishwashers,

washing machines 

do not require a 

minimum temperature

for optimum cleaning.

100120 140

vc-cd14-a1242-05

Setting the thermostat on 

your water heater to 120 ̊F,

which is sufficient for most

household needs, is an

energy-saving measure you

may wish to consider.
Install a Timer and Heat Traps

Another possibility for electric water

heaters is installing a timer that can automatically turn the heater off at night and

on in the morning. At a $30 selling price

and a do-it-yourself installation, a simple

timer may pay for itself in energy saved in

about 1 year. More expensive, multisetting

timers are also available. Timers for gas

water heaters are not as useful or cost

effective as those designed for electric

water heaters. This is because the pilot

light supplies some heat during the night,

offsetting some of the energy savings

achieved by using the timer.

If heat traps were not initially installed

with your water heater, adding them is

another way of reducing water-heating

energy loss. Heat traps, or one-way

valves, allow water to flow into the tank

and prevent unwanted hot-water flow out

of the tank. Heat traps cost about $30, but

they may require professional installation,

which could be expensive. However, if

installed at the same time as a new water

heater, heat traps are much more cost effective. Most new water heater models have

factory installed traps, saving you the time

and expense of installing one yourself.

Insulate Hot-Water Pipes 

and the Storage Tank

When you turn on a hot-water faucet during cold weather, it may take several seconds for the water to become hot. This

happens because the water travels through

pipes from the water heater to the faucet,

and some of the pipes may pass through

unheated sections of the house, such as the

basement. As a result, the hot water loses

some of its heat to the surrounding space.

This heat loss can be reduced by insulating

hot water pipes wherever they are accessible—especially in unheated areas. Use

quality pipe insulation wrap, or neatly

tape strips of fiberglass insulation around

the pipes. Eventually the water will cool,

but it will remain warmer much longer

inside insulated pipes.

Insulating your water-heater storage tank

is a fairly simple and inexpensive improvement that can help maintain the water

temperature at the thermostat setting.

Some newer models of water heaters are 

well insulated and do not need an added

layer, but a heater that is warm to the

touch needs additional insulation.

Easy-to-install, pre-cut blankets (or jackets) for electric water heaters are widely

available and range in cost from $10 to

$20. Your local utility company may offer

them at a lower price, give you a rebate, or

even install them at no cost. When properly installed, a water heater blanket on 

an electric water heater will pay for itself

in energy saved within 1 year. Installation

is more difficult on gas- and oil-fired

heaters. Ask your local furnace installer

for instructions.

If your water heater is at least 7 years old,

you should carefully evaluate your waterheating needs and investigate the types of

heaters that could replace your current

one. Although most water heaters last 10

to 15 years, early investigation and timely

replacement can ensure a wiser purchase.

For more information on the types of

water heaters now available, contact the

Energy Efficiency and Renewable Energy

Clearinghouse (EREC—see Source List).

Using Off-Peak Power to 

Heat Water

Most consumers use more hot water in the

evenings and mornings than at other

times of the day. For those who have an

electric water heater, this usage contributes to the electric utility company’s

“peak load,” or the largest amount of

power demand that they have to meet on

a daily basis. Some utilities are required 

to offer their customers “time of use” rates

that vary according to the demand on

their system. Lower rates may be charged

at “off-peak” times and higher rates at

“on-peak” times. You may be able to 

lower your electric bills if you can take

advantage of these rate schedules. Check

with your local electric utility to find out 

if it offers time-of-use rates for residential

customers, and if so, what the rate schedules are. Some utilities even offer incentives for customers who allow their 

utility to install control devices that shut

off electric water heaters during peak

demand periods.

4

vc-cd14-a1242-06

Timers that automatically turn

your water heater off and on

are a good energy-saving

option if you have an electric

water heater.

Heat

traps

vc-cd14-a1242-07

Heat traps, or one-way 

valves, can control the flow 

of water into and out of your

storage tank.
5

Installing an 

Insulation Blanket on an 

Electric Water Heater

Note: Installation is more difficult on gasand oil-fired heaters. Ask your local furnace installer for instructions.

1. Cut the tank top insulation to fit around

the piping in the top of the tank. Tape the

cut section closed after the top has been

installed.

2. Fold the corners of the tank top insulation down and tape to the sides of the tank

(Figure 1).

3. Position the insulating blanket around

the circumference of the tank. For ease of

installation, position the blanket so that

the ends do not come together over the

access panels in the side of the tank. Some

tanks have only one access panel.

4. Secure the blanket in place with the

belts provided. Position the belts so they

do not go over the access panels (Figure 2).

Belts should fit snugly over the blanket

but not compress it more than 15% to 20%

of its thickness. The installation is easier

with two people. If working alone, use

tape to hold the blanket to the top until

you get the belts into position.

5. If your water heater has the temperature/pressure relief valve and the overflow pipe on the side of the tank instead 

of on the top, install the blanket so these

items are outside of the blanket. Depending on the piping arrangement and location, you may need to compress, or even

cut, the blanket.

6. Locate the four corners of the access

panel(s). Make an x-shaped cut in the

insulating blanket from corner to corner of

each access panel (Figure 3).

7. Fold the triangular flaps produced by

the cuts underneath the insulating blanket

(Figure 4). Repeat steps 6 and 7 for the rating/instruction plate.

8. The blanket must not be installed on a

leaking tank.

  

   

   

  

   

Simple Actions, Big Results

Some ways to save on water-heating bills

require greater financial investments 

than others. You may wish to consider 

the no- or low-cost options before making

large purchases. Also allow for circumstances that may be unique to your household when deciding on the appropriate

options (e.g., a small-capacity washing 

machine could meet the needs of a oneperson household efficiently). 

Although it is not feasible to eliminate

water heating in your home, it is possible

to substantially reduce water-heating costs

without sacrificing comfort and convenience. The tips in this publication can

help decrease your costs for heating water.

1 2

3 4
Source List

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,

California.

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.

Gas Appliance Manufacturers Association, Inc. 

(GAMA)

1901 North Moore Street, Suite 1100

Arlington, VA 22209

(703) 525-9565

GAMA has information on residential gas appliances and

equipment, electric and oil-fired water heaters, and oil-fired

warm air furnaces.

U.S. Department of Energy

Energy Information Administration (EIA)

National Energy Information Center

EI-231, Room 1F-048

Forrestal Building

Washington, DC 20585

(202) 586-8800

EIA compiles a wide range of statistics for the energy professional on energy sources and energy consumption. EIA’s

Household Energy and Consumption and Expenditures contains

information on residential energy use.

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

(800) 363-3732

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 

and utility for additional information on energy-efficient

water heaters, installation, and rebate or incentive programs.

Reading List

Books and Reports

Consumer Reports 1992 Buying Guide Issue, Consumers

Union of the United States, Inc., 101 Truman Avenue,

Yonkers, NY 10703-1057, December 1991.

The Water Heater Workbook: A Hands-on Guide to Water

Heaters, published by Elemental Enterprises, P.O. 

Box 928, Monterey, CA 93942, 1992.

“Water Heating,” Energy Edge, Pennsylvania Energy

Office, 116 Pine Street, Harrisburg, PA 17101 (printed 

by DOE).

Articles

“An Investigation of Off-Peak Domestic Hot Water 

Heating,” ASHRAE Journal, p. 32, January 1990.

“Dishwashers,” Consumer Reports, p. 637, October 1993.

“Hot Water Energy Conservation: Heating Water

Accounts for 15% to 25% of an Average Family’s Energy

Budget,” Consumer’s Research Magazine, p. 19, 

January 1991.

“Safer Water Filters, Cheaper Water-Heating Systems,

and More,” Home Mechanix, p. 37, June 1993.

“Showering Them With Gas,” American Gas, p. 22, 

April 1989.

6