Water Heaters

Water Heater Types
It’s a good idea to know the different types of water heaters available before you purchase one:
  • Conventional storage water heaters offer a ready reservoir (storage tank) of hot water
  • Tankless or demand-type water heaters heat water directly without the use of a storage tank
  • Heat pump water heaters move heat from one place to another instead of generating heat directly for providing hot water
  • Solar water heaters use the sun’s heat to provide hot water
  • Tankless coil and indirect water heaters use a home’s space heating system to heat water
Selection Criteria
When selecting the best type and model of water heater for your home, consider the following:
  • Fuel type, availability and cost. The fuel type or energy source you use for water heating will not only affect the water heater’s annual operation costs but also its size and energy efficiency. See below for more on selecting fuel types.
  • Size. To provide your household with enough hot water and to maximize efficiency, you need a properly sized water heater. Visit the pages on different types of water heaters (linked above) for more on sizing.
  • Energy efficiency. To maximize your energy and cost savings, you want to know how energy efficient a water heater is before you purchase it. Visit the pages on different types of water heaters (linked above) for more on estimating energy efficiency.
  • Costs. Before you purchase a water heater, it’s also a good idea to estimate its annual operating costs and compare those costs with other less or more energy-efficient models. Visit the pages on different types of water heaters (linked above) for more on estimating costs.
Also be sure to do what you can to reduce your hot water use. You may also want to explore other strategies such as drain-water heat recovery to save money on your water heating bill.
Fuel types, availability and costs for water heating
When selecting a new water heater, it’s important to consider what fuel type or energy source you will use, including its availability and cost. The fuel used by a water heating system will not only affect annual operation costs but also the water heater’s size and energy efficiency.
Fuel type and its availability in your area may narrow your water heater choices. The following is a list of water heater options by fuel or energy source:
  • Electricity. Widely available in the United States to fuel conventional storage, tankless or demand-type, and heat pump water heaters. It also can be used with combination water and space heating systems, which include tankless coil and indirect water heaters.
  • Fuel oil. Available in some areas of the United States to fuel conventional storage water heaters, and indirect combination water and space heating systems.
  • Geothermal energy. Available throughout the United States to those who will have or already have a geothermal heat pump system installed in their homes for space heating and cooling. See Heat Pump Water Heaters for more information.
  • Natural gas. Available in many areas of the United States to fuel conventional storage and demand (tankless or instantaneous) water heaters, as well as combination water and space heating systems, which include tankless coil and indirect water heaters.
  • Propane. Available in many areas of the United States to fuel conventional storage and demand (tankless or instantaneous) water heaters, as well as indirect combination water and space heating systems.
  • Solar energy. Available throughout the United States — most abundantly in the Southwest — for solar water heaters.
Comparing fuel costs and water heater types
If you have more than one fuel type available in your area, it’s a good idea to compare fuel costs, especially if you’re building a new home. Even if you’re replacing a water heater, you may find that you’ll save more money in the long run if you use a different fuel or energy source. Contact your utility for current fuel costs or rates.
The type of water heater you choose will also affect your water heating costs. One type of water heater may use a fuel type more efficiently than another type of water heater. For example, an electric heat pump water heater typically is more energy efficient than an electric conventional storage water heater. Also, an electric heat pump water heater might have lower energy costs because of its higher efficiency than a gas-fired conventional storage water heater, even though local natural gas costs might be lower than the electricity rates.
Dept. of Energy
Water Heater Tips
  1. Repair leaky faucets promptly; a leaky faucet wastes gallons of water in a short period.
  2. Insulate your electric hot-water storage tank and pipes, but be careful not to cover the thermostat.
  3. Insulate your gas or oil hot-water storage tank and pipes, but be careful not to cover the water heater’s top, bottom, thermostat, or burner compartment; when in doubt, get professional help.
  4. Install non-aerating low-flow faucets and showerheads.
  5. Buy a new water heater. While it may cost more initially than a standard water heater, the energy savings will continue during the lifetime of the appliance.
  6. Although most water heaters last 10-15 years, it’s best to start shopping for a new one if yours is more than 7 years old. Doing some research before your heater fails will enable you to select one that most appropriately meets your needs.
  7. Lower the thermostat on your water heater; water heaters sometimes come from the factory with high temperature settings, but a setting of 115°F provides comfortable hot water for most uses.
  8. Drain a quart of water from your water tank every 3 months to remove sediment that impedes heat transfer and lowers the efficiency of your heater. The type of water tank you have determines the steps to take, so follow the manufacturer’s advice.
  9. If you heat with electricity and live in a warm and sunny climate, consider installing a solar water heater. The solar units are environmentally friendly and can now be installed on your roof to blend with the architecture of your house.
  10. Take more showers than baths. Bathing uses the most hot water in the average household. You use 15-25 gallons of hot water for a bath, but less than 10 gallons during a 5-minute shower.
Water Heater FAQs
What is the average lifetime of a gas water heater?
The average lifetime of gas water heater is 9 years. The range is 5-14 years.
How is FHR and Therms used to compare the efficiency of water heaters?
The first hour rating (FHR) tells you the number of gallons per hour of hot water. Therms relate to the gas consumption of water heater. When you are shopping for hot water heater, compare the energy factor on the energy guide label. FHR and Therms are not sufficient to calculate the energy factor. Also remember to compare water heaters of equal capacity and FHR.
What efficiency standard does a dual use residential water heater need to meet as a water heater or a boiler (used for both potable water and space heating purposes)?
For a dual unit, it must meet the efficiency standard requirements of both applications. Your local building department may have additional requirements for such units.
What is a hot water recirculating system?
A “hot water re-circulating” system usually refers to a domestic hot water system that circulates the heated water through the house continuously so as to eliminate or shorten the delay in hot water reaching the faucet after the user turns it on. These systems are most common in multifamily or large building applications where otherwise the delays would be truly unacceptable. They can be real energy hogs if the pipes aren’t well insulated.
How do I choose the best electric or gas tankless water heater for my home (2300 sq. ft.)?
Sizing of hot water heaters should be based on the number of occupants and their peak hour water demand and not on the size of the house.
Are tankless water heaters more efficient?
Tankless water heater efficiencies are not addressed by the Federal standards. Check the EREC fact sheet for additional resources.

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