ENERGY STAR® – Qualifying Criteria for Residential Boilers (Gas-Fired, Oil-Fired)


Residential Boiler – categorized as a self-contained fuel burning appliance with an energy input of less than 300 000 Btu per hour, for supplying low-pressure steam or hot water for space heating applications. A heating unit that meets this definition and also provides hot water for domestic or other use is considered a boiler.

Test Standards

CGA P.2-1991 (Gas-Fired Boilers) CAN/CSA -B212-M93 (Oil-Fired Boilers)


ENERGY STAR-labelled boilers must meet or exceed 85-percent AFUE* energy efficiency ratings.

*Annual Fuel Utilization Efficiency (AFUE): A measure of the amount of fuel converted to space heat in proportion to the amount of fuel entering the boiler. This is commonly expressed as a percentage.

Boilers designed for space heating can also provide domestic hot water for residential applications. There are two basic methods used:

  1. Indirect storage. These well-insulated tanks operate as a separate heating zone with substantially reduced heat losses and higher efficiencies as compared to tankless coils.

  2. Tankless coil. Operating a boiler with a tankless coil will reduce the overall energy efficiency of the boiler.