AFUE

Metrics and Efficiency Ratings - HVAC Costs pillar

Also known as: Annual Fuel Utilization Efficiency

Annual Fuel Utilization Efficiency. The percentage of fuel a furnace converts to usable heat over a heating season. Modern condensing gas furnaces sold in Canada must be at least 95% AFUE.

AFUE measures the seasonal-average efficiency of a furnace or boiler. An 80% AFUE furnace turns 80 cents of every fuel dollar into heat; the remaining 20 cents goes up the flue. Canada's Energy Efficiency Regulations require new gas furnaces to be at least 95% AFUE, which means they must be condensing units (extracting latent heat from flue gas water vapor). Pre-2010 80% AFUE furnaces in Ontario homes typically waste 15% or more energy versus modern equipment.

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