Domestic Hot Water - Single Family Housing

The domestic hot water system you install will depend on the fuel type available and usage needs in the household. There are several types to choose from, each with a different efficiency range. Multifamily buildings have different requirements than single family housing.

Types of Water Heaters Available

Water heaters available include conventional storage, demand, heat pump, tankless coil, indirect, and solar.

• 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.
• Demand (or instantaneous) water heaters 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 when needed.
• 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.
• Two types of water heaters use a home's heating system: tankless coil and indirect. In the tankless coil, 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. The indirect water heater circulates water through a heat exchanger in the boiler. This heated water then flows to an insulated storage tank.
• Solar water heaters include a collector and a storage tank and are typically classified as passive or active systems. These systems often use a conventional heater as backup.

More about Water Heater Types from the Department of Energy.

Factors to Consider

The Energy Factor (EF) of the water heater will tell you the efficiency of the unit. The systems available are electric resistance water heaters with an EF in the range of 0.7 to 0.95, gas water heaters with an EF of 0.5 to 0.62, oil water heaters ranging from a 0.7 to 0.85 EF, gas condensing and gas tankless water heaters with an EF of 0.8 and above, and heat pump water heaters with the highest efficiency and an EF of 1.5 to 2.0. Energy efficiency can be compared on each unit by the EnergyGuide labels on the tank.

Another important factor when comparing water heaters is the First Hour Rating, FHR. The first hour rating measures how much hot water the heater will be capable of delivering during the hour of highest use. Estimating your peak hot water usage will help you identify an appropriate tank for your household or facility.

Insulation

If you are not ready to purchase a new water heater but would like to improve the one you currently have, consider installing a heavy insulation blanket on it to achieve a rating of R-16. Take into consideration that some older heaters have insulation rated R-7, therefore a minimum of R-9 rated blanket would be necessary to add.

All fittings should be dry and in good shape before installing the wrap. You can also obtain a Gas Appliance and Manufacturer's Association (GAMA) safety sticker from GAMA or a plumber and it should be placed on the blanket. Leave the anode, relief valve and controls accessible for routine maintenance. Also, keep in mind that the blanket should not restrict access to the controls or the openings for combustion air.

Control

Timers and heat traps may be installed for better control. This will save you by automatically turning the heater off at night and on in the morning when the hot water is needed. Timers typically cost about $30 and can be installed yourself. Timers are appropriate for electric models. Gas models have a pilot light that is constantly burning anyway so at timer will not help save fuel. Heat traps also reduce energy consumption by reducing heat loss. They are essentially one-way valves that prevent hot water from flowing out of the tank and water that may be sitting in the pipes from flowing back into the water heater. These may also cost only $30 but require a professional to install.

Multifamily Domestic Hot Water