Water Heater Manuals & Owner Guides

Water heater types

Heat pump (hybrid)

Moves heat from the surrounding air into the tank, using a fraction of the electricity of a standard electric heater. Integrated units need space and air; split units put the heat pump outdoors.

Gas tankless

Heats water only when a tap opens. Endless hot water within its flow rating, but needs a large gas line and periodic descaling.

Gas storage

A tank kept hot by a gas burner. ENERGY STAR models are high-efficiency condensing designs with powered venting.

Solar

Rooftop collectors preheat water, with a gas or electric backup for cloudy weather.

Sizing: first-hour rating and flow rate

For storage and heat pump models, size by the first-hour rating (FHR): the gallons of hot water the heater can deliver in one busy hour. For tankless models, size by gallons per minute at your winter temperature rise. A typical shower uses about 2 gpm; a household that runs two showers at once in winter needs a tankless unit that can supply 4 gpm or more at an 80 °F rise.

Understanding UEF

The Uniform Energy Factor (UEF) compares the energy delivered as hot water with the energy the heater uses over a standard day. Typical values: about 0.6 for a basic gas tank, 0.9–0.95 for standard electric tanks and condensing gas models, and 3 to 4 or more for heat pump water heaters. Compare models only within the same draw pattern.

Water Heater FAQ