​​Natural Gas Water Heaters

Natural gas water heaters are safe and energy efficient.

From relaxing in a hot bath to cleaning a load of the kids' school clothes, you rely on a safe, reliable supply of hot water for many everyday activities. Today's natural gas water heaters represent an extraordinary value in performance, reliability and operating costs, making them the choice of energy-conscious homeowners.​

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The benefits of efficient natural gas water heaters

Natural gas water heaters offer many benefits:

  • Quick recovery: Natural gas water heaters heat water fast so you have the hot water you need, when you need it.
  • Lower operating costs: Natural gas water heaters provide hot water efficiently so you save on operating costs. Save even more when you choose a high-efficiency model rather than a standard-efficiency unit.
  • Excellent safety record: Natural gas water heaters have been safely providing hot water in millions of homes for years. They stand on their safety record.
  • Save space: Faster recovery rates for natural gas water heaters means you can use a smaller tankand save space. Or, opt for a compact tankless water heater​.
  • Installation options: There is a natural gas water heater for every situation whether you are building a new home or simply remodeling.
  • Environmentally friendly: When energy conservation and environmental issues are a primary concern, clean-burning natural gas water heaters are the best way to heat water.
  • Reliability: Natural gas water heaters are so reliable and easy to maintain that most people never think about their water heater, even though they use hot water several times a day.

Shopping for a natural gas water heater

When shopping for a natural gas water heater, you should consider:

  • Purchase price vs. energy efficiency
  • Size

Purchase price vs. energy efficiency

Water heating accounts for about 15% of your home's energy use so, when shopping for a water heater, it's important to choose an efficient model.

Although the purchase price may be a little higher for a more energy efficient water heater, remember, you will usually regain that extra cost and sometimes more in energy savings throughout the life of the unit. Operating costs with gas are typically about 50% lower than with electric; savings will vary depending on fuel costs and unit efficiency.

  • You can judge the efficiency of a water heater by its Energy Factor (EF)*. The higher the EF number, the higher the efficiency and the lower the operating costs.
  • Usually natural gas water heaters have an Energy Factor between .53EF and .58EF*, with the highest ratings going above .62EF up to .65EF.
  • Tankless natural gas water heaters range from .83EF to .95EF.

*EF, Energy Factor, is the ratio of annual useful energy in the heated water to the annual water heater energy consumption, i.e. the energy going into the water heater.


A properly sized water heater will deliver the hot water you want when you need it. There are two ways to determine the appropriate size water heater for your home – a general method and the first-hour rating method.

General method

The first method depends on the number and ages of family members, how you wash dishes and clothes, and the number of bathrooms in your home.

  • Usually the needs of a family of two with one bathroom and a clothes washer should be adequately met with a 30-gallon gas water heater.
  • For every additional bathroom in your home, add another 3-1/2 gallons to the tank capacity.
  • If you use an automatic dishwasher, add another five gallons to this total.
  • These are general guidelines since no two families' hot water use are exactly alike. Keep in mind your family's lifestyle and habits when estimating your family's hot water needs.

First-hour rating

The second method to consider is the "first-hour rating". It will tell you the amount of hot water the water heater can deliver in one hour. Follow this procedure to use the first-hour rating:

  • Determine the hour of the day when you use the most water.
  • Use the following chart to find the quantity of hot water you use for each activity during that hour.
  • Add all the quantities for that hour. The total is your first-hour rating.Choose a water heater with a first-hour rating close to the total amount of hot water you use during the hour you selected. The first-hour rating also includes the "recovery rate." This is a combination of how much water is stored in the water heater and how quickly the water heater can heat cold water to the desired temperature.
Activity Hot water used 
Automatic washer 25 to 40 gallons per load
Non-automatic washer10 to 20 gallons per load
 Dishwasher5 to 10 gallons per load
Hand dishwashing 3 to 4 gallons
Tub bath15 to 25 gallons
Shower bath3 gallons per minute
Bathing an infant2 gallons
​Shaving2 to 3 1/2 gallons
Shampooing5 gallons
Hand washing
1 to 2 gallons
House cleaning
5 to 12 gallons
Food preparation
3 to 6 gallons

New options in natural gas water heaters

Whether you are replacing an existing water heater, remodeling, or building a new home, there is a natural gas water heater to meet the needs of your situation. The following list of water heater options includes the basic atmospheric-vent unit, as well as the newest options in gas water heaters including the power-vent, direct-vent, powered direct-vent, tankless and combination systems.


These are the standard gas water heaters that have been serving millions of homeowners for years. They use room air for combustion and exhaust. The exhaust chimney is installed to a draft hood that sits slightly above the tank. These water heaters use "gravity" (rising warm air) to exhaust combustion byproducts and are vented through the roof. Typically the exhaust vent is connected to the furnace vent and they share the same chimney.

  • Benefits: all the benefits of natural gas water heating including a compact unit design, quick recovery, an excellent safety record, low operating costs, high efficiency, and environmental friendliness.


Direct-vent units use no room air at all. Direct-vent water heaters are particularly good for tight construction because they use outside air versus room air for both combustion and exhaust, so they operate independently of other exhaust systems in the house.​

Tankless water heaters

Tankless water heaters provide hot water on demand without the use of a storage tank. A tankless water heater has a gas burner that is activated by the flow of water whenever a hot water faucet is turned on. The water heater will deliver a constant supply of hot water until the faucet is turned off. Learn more about tankless water heaters.​

Combination systems

These dual-purpose models feature a tank within a tank, one providing hot water for the family and the other providing warm water for space heating such as a radiant floor system. They offer increased energy efficiency and reduced costs for whole house or room heating plus all the benefits of natural gas water heating.

Make sure your water heater is installed by a licensed plumber or service person according to local codes and manufacturer's instructions.​

Flammable vapors ignition resistant gas water heaters

In July 2003, manufacturers began adding flammable vapor ignition resistance technology to 30 – 50 gal. atmospheric-vent natural gas water heaters. The added safety measure, required by the federal government, helps prevent fires or explosions from vapors being ignited by the units. While such incidents are rare, especially in cold weather areas where water heaters are located inside the home rather than in garages, the new technology makes these models even safer. The same update is now required for 30 – 50 gal. power-vented units and all other models.​

How a natural gas water heater works

A water heater is a thermostat-controlled storage tank that heats water and keeps it warm. It operates continuously and automatically, beginning when cold water is delivered to the bottom of the tank through the dip tube. The thermostat senses the cold water and calls for the burner to ignite. The burner brings the water to the desired temperature; the thermostat then shuts off the main burner until the stored water temperature again calls for heat.​

Safe water temperatures

For best results...

  • Turn your water heater thermostat to the lowest setting comfortable for you and your family. For most people, 120°F is sufficient and safe. However, these lower water temperatures may affect automatic dishwashing and laundering. Although manufacturers of this equipment usually recommend 140°F for best results, a lower temperature may also give satisfactory results.

When buying a new dishwasher, look for models that heat water themselves to 140°F. This allows you to lower the temperature setting on your home's central water heater to 120°F.​

Caring for your natural gas water heater

  • Keep the burner area free of dust and dirt.
  • Store combustibles or flammables such as gasoline or paint away from the water heater.
  • A gurgling noise when the burner is on is a sign of sediment buildup which can damage your water heater. To keep lime deposits and sediment from building up in your water heater, starting when it's new, every month drain several pails of water from the drain valve near the bottom of the water heater. CAUTION: An older water heater which has not been regularly drained may already have lime deposits that make it impossible to completely close the drain valve after draining water from the tank as suggested. It may also cause a constant drip.
  • Relighting the pilot light: If the pilot light on the water heater goes out, shut off gas to the appliance. Do not use tools to turn the gas valve; use hand pressure only. Relight according to manufacturer's instructions, usually near the control on the lower part of the tank. If you have difficulty relighting, call a qualified appliance service technician or qualified heating contractor.

Energy-saving tips

The best way to reduce energy use for water heating is to use less hot water.

  • When doing laundry, use the shortest wash cycle, the lowest water temperature possible and a cold rinse.
  • Scrape dishes before placing in the dishwasher. Use cold water for rinsing. If washing dishes by hand, turn rinse water on and off as needed.
  • Take short showers rather than baths. Install a flow-restricting or low-flow showerhead, which can reduce flow by about 50%.
  • Promptly repair leaky faucets. A leak that fills a coffee cup in 10 minutes wastes 3,280 gallons of water a year.
  • Never let water run continuously while brushing your teeth or shaving.
  • When you need only a little water from the tap, use cold water. Hot water drawn into the pipes may never reach the tap and the heat is wasted.
  • Wrap insulation on long stretches of pipe between your water heater and the point of use, and on pipes running through unheated areas.
  • Natural Gas Water Heaters fact sheet (PDF)*

For more ways on how you can save energy at home, see a list of energy-saving programs and tips.