The U.S EPA sets minimum efficiency standards for appliances such as heating and cooling equipment.
- Many older furnaces still operating and functioning well have efficiencies between 70% and 75%.
- Furnaces installed after 1992 must have efficiency ratings above 78%.
- Modern, high-efficiency furnaces have ratings in the mid-90%.
Heating systems with leaky, uninsulated ducts or that are improperly sized can reduce even a high-efficiency furnace to an efficiency of under 65%.