Efficiency Ratings
SEER2, EER2, HSPF2, AFUE, COP and CADR explained in plain terms, with what each rating means for your bills.
Calculators
Guides
AFUE Rating Explained: 80% vs 90–98% Furnaces and What You SaveAFUE (Annual Fuel Utilization Efficiency) is the percentage of a furnace's fuel energy that ends up as heat in your home…CADR Rating Explained: Smoke, Dust and Pollen Numbers by Room SizeCADR (Clean Air Delivery Rate) is the volume of particle-free air a portable air purifier delivers, in cubic feet per mi…EER Rating Explained: EER vs EER2 and Why Peak-Heat Efficiency MattersEER is cooling output in BTU/h divided by power input in watts at one fixed hot condition: 95 °F outdoors with 80 °F, 67…Heat Pump Efficiency vs Temperature: COP Chart, Balance Point and DefrostA heat pump's COP falls as the outdoor temperature drops, because it must lift heat across a bigger temperature gap. Typ…HSPF Rating Explained: HSPF vs HSPF2 and Seasonal Heat Pump COPHSPF is the total heat a heat pump delivers over a modeled heating season, in BTU, divided by the watt-hours it uses, in…