UEF

Metrics and Efficiency Ratings - Water Heaters pillar

Also known as: Uniform Energy Factor

Uniform Energy Factor. The 2017+ water heater efficiency rating that replaced EF, accounting for standby losses and recovery in a 24-hour test.

UEF replaced Energy Factor (EF) in 2017 as the federal water heater efficiency metric. UEF is the ratio of useful hot water energy delivered to total energy consumed across a standardized 24-hour simulated-use test. Higher = better. Federal minimums: gas storage tank 0.64 (50 gal), electric storage tank 0.92 (50 gal). ENERGY STAR cutoffs: gas 0.81, condensing tankless 0.87, heat pump water heater 2.0+. The UEF on the EnerGuide label is the apples-to-apples number for comparing quotes.

See the full Ontario HVAC and home energy glossary or browse the Water Heaters pillar.