Energy Factor ratings allow homeowners and contractors to compare the efficiencies of different water heaters. A water heater that uses 62% of the energy it consumes has a .62 Energy Factor (EF). Standard gas-powered water heaters require an EF of at least .67 in order to have the chance to achieve Energy Star status. .82 is the minimum EF a tank-style gas or oil water heater must have in order to qualify for a U.S. tax credit in 2011.
EF ratings are not available for tank-style water heaters with BTU inputs over 75,000 BTUs (200,000 BTUs on tankless units). See the water heater section on SupplyHouse.com for units from A.O. Smith, Bradford White, and Takagi.
