Gas Furnace Efficiency & How to Measure It

Does effective gas furnace efficiency matter? It's the difference between wasting hundreds or thousands of dollars on fuel you don't need and keeping that money in your wallet. Depending on where you live, it can determine whether you qualify for cash rebates, zero-interest financing, or other incentives. And for the eco-conscious, better efficiency means you consume fewer fossil fuels to get the comfort you want.

How to Determine Your Gas Furnace Efficiency

Essentially, there is no good reason not to invest in high gas furnace efficiency. Yes, a lower efficiency unit is cheaper up front, but the extra money you'll spend over the long term cancels out that lower price tag.

So, how can you tell a high efficiency system from an average or low one?

All furnaces in the United States are rated according to their Annual Fuel Utilization Efficiency (AFUE). The higher the AFUE, the more efficiently the furnace burns its fuel. There is no such thing as perfect gas furnace efficiency, so the highest rating you will find is around 98%.

As you might imagine, a 98% efficient furnace is a very, very good one. In fact, anything above 90% is considered above average. 90% or more will save you a bundle compared to the industry average, and a huge amount versus outdated, previous generation systems. If you're still using a decades old system with low efficiency, now is the time to upgrade.

But what's average? The lowest efficiency rating you can legally install in the USA is 80% AFUE. Which is better than most furnaces built in the 20th century, but it's still not great. 80% AFUE means that for every dollar you spend buying gas you're just throwing away 20% of it.

Which is something you would never do anywhere else. Can you imagine bringing home a gallon of milk and dumping 20% of it down the drain? Or hacking 20% off a steak and tossing that in the trash?

No, that would be silly, so make sure your gas furnace efficiency is way better than silly.

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