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.”
Let’s dig deeper into the 100% AFUE rating
Efficiency simply means how much of the heating system’s energy supply is converted to thermal output. A gas furnace will always waste some of its natural gas through the process of combusting it and then transferring it to the air through the heat exchanger. With an electric furnace, the electricity is directed through a series of seven heating elements inside the furnace, heating them up to warm the air. No electricity goes to waste in this process; all of it is used. That’s why an electric furnace has an AFUE rating of 100%.
Here’s the big difference: the cost of the energy supply. Electricity is a more expensive energy source than natural gas because electrical plants use coal, gas, or oil generators, and they often waste around 30% of their energy. Electricity doesn’t come from out of nowhere! And in order for an electric furnace to become hot enough to warm up the air moving through it and make a home comfortable in a freezing Chicago winter, it must consume a great deal of electricity.
A gas furnace, on the other hand, doesn’t need to consume a tremendous amount of natural gas to generate high heat levels. Natural gas also costs less because it only needs to be refined before it’s sent to a home. Even a natural gas furnace with an AFUE rating of 80% (lower than the minimum set by the Department of Energy) will cost less to run than a 100% AFUE electric furnace.
An Electric Alternative
We aren’t saying that an electric furnace should be completely off the table when it comes to picking a heating system. We simply want you to be informed about what the efficiency rating really means in this case, and what you can expect in terms of cost for gas vs. electric.
If your home has no connection to a natural gas line, and electric furnace is definitely an option to look into. But we recommend you give consideration to a heat pump. A heat pump uses smaller amounts of electricity for heating because it doesn’t use the electricity to directly generate heat. Rather, it powers components that move heat from one place to another. This can mean a 50% drop in heating costs compared to an electric furnace.
Brilliant Home Services: Servicing Chicagoland since 1956.