Last week we discussed how the efficiency ratings for furnaces work. The short version: a gas furnace’s efficiency is rated as AFUE (annual fuel utilization efficiency), a percentage that tells you how much of the furnace’s natural gas fuel supply it converts into heat. The current ENERGY STAR requirement for furnaces is 90% AFUE or above.
“Okay, but what about electric furnaces?” you might ask. “How do they score on AFUE?”
It’s good question. And the answer is a deceptive one: electric furnaces have 100% AFUE.
“So I should always get an electric furnace, right? Even the highest end gas furnace doesn’t get 100% AFUE! An electric furnace has a perfect score!”
Okay… this is one of difficulties in explaining AFUE to people unfamiliar with it. AFUE doesn’t actually tell you how much you’ll pay to run your furnace. “Higher Efficiency” isn’t equal to “Lower Cost.”