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Cool Touch Air Conditioning and Heating Blog

Understand the Electric Furnace AFUE Rating

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When it comes to heating homes, electric furnaces are common in Arizona. We don’t rely on heating systems as much in our warmer climates, and electric furnaces are effective ways to provide warmth in these conditions. They’re smaller than gas furnaces, cost less to install, and don’t take up much space.

However, there’s some confusion people have about the cost to run an electric furnace compared to a gas furnace, and that’s due to their AFUE ratings. We’re going to look into this confusion in this post to help you better understand how an electric furnace works.

AFUE Is a Heating Efficiency Rating

AFUE stands for annual fuel utilization efficiency, and it’s the government standard developed to measure how efficiently a heating system converts its energy source into heating output. It’s used to measure the efficiency of furnaces and boilers. (Heat pumps use a different efficiency rating for heating mode, HSPF.) 

AFUE is a percentage of how much of its energy source a heating system converts directly into heating output, with the remainder lost to exhaust. For example, old mid-efficiency gas furnaces averaged around 70% AFUE. For every 100 units of fuel, the furnace would convert 70 units to heat and lose 30 to exhaust. Today’s gas furnaces usually rate much higher: the ENERGY STAR program requires gas furnaces to have an AFUE of 90% or more, while condensing gas furnaces can score above 95% AFUE.

Electric Furnaces Have 100% AFUE

You read that right. All electric furnaces have a 100% AFUE rating. They convert all their energy into heating and lose nothing to exhaust. That makes sense, because electric furnaces don’t burn fuel and create exhaust. An electric furnace operates by running electricity through coils that heat up through electrical resistance. All the energy converts straight to heating power and nothing is lost.

But … does that mean an electric furnace is cheaper to run than a gas furnace? No. This is where “efficiency” becomes tricky. Getting a high-efficiency heating system of any type is never a guarantee of energy savings. There are other factors involved that can cause the heating system to use more power even with higher efficiency. In general, if you have an old gas furnace with 75% AFUE and you upgrade to a new 90% AFUE furnace, you’ll save money (provided professionals installed it). But switching to an electric furnace probably won’t save you energy.

The reason is the cost of electricity vs. the cost of natural gas. An electric furnace may not waste any of the electrical power it uses, but it has to consume a great deal of electricity to generate heat, and electricity is often more expensive than natural gas. That 100% AFUE rating doesn’t mean much in this comparison; it’s more useful to compare the AFUE of gas furnaces and oil furnaces to each other.

Thankfully, because we don’t keep our furnaces running for long in Arizona, using an electric furnace won’t usually cost a house too much more than a gas one. Our technicians can help you make the best choice for your home heating installation in Glendale, AZ.

Call Cool Touch Air Conditioning and Heating: Kick Back and Relax, We’ll Keep You Cool (or Warm).

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