What does AFUE Mean? What is an AFUE Rating?

What does AFUE Mean? What is an AFUE Rating?

gas or propane furnace enAFUE is an acronym for Annual Fuel Utilization Efficiency, the most straightforward measure of furnace efficiency.

A more efficient furnace will cost more at the initial point of purchase, but will save money on each utility bill for the next 20 years.

Air conditioners have SEER (Seasonal Energy Efficiency Rating), which more or less measures the same thing. Where SEER ratings are assigned somewhat arbitrary numbers, AFUE ratings are clear percentages. If a furnace is rated AFUE 80, it means 80% of the fuel put into the furnace returns to your home as heat.

Fuel efficiency ratings

Different fuels achieve varying levels of efficiency.




Electricity Baseboard 100%
Natural Gas Mid to High Efficiency 80-97%
Propane Mid to High Efficiency 85-95%
Firewood Fireplace 50-55%

But if you’re concerned with cost, efficiency isn’t your only measure. Electricity heats with a 100 AFUE rating, but that doesn’t mean it will be more affordable to run than a natural gas or propane furnace.

In fact, a new, high AFUE furnace might not be cheaper to run than your existing furnace

gas billThe type of fuel used in your furnace is the largest factor affecting your monthly heating bills. An electric heater will outperform a propane furnace handily in efficiency, but can’t hope to ever beat the cost of a propane furnace to operate. Propane furnaces will always be more affordable to operate than electric heaters.

AFUE is a great way to measure two furnaces of the same fuel type against each other. A ClimateCare TP9C model natural gas furnace at 98 AFUE will be far more affordable to operate than a Carrier natural gas furnace at 84 AFUE.

However, AFUE could not accurately measure an electric Carrier furnace at 100 AFUE against a ClimateCare TM9E series furnace at 95 AFUE.

Umm, why?

Because all fuel is not equal! The Carrier electric at 100% efficiency will still cost significantly more to run than the ClimateCare furnace.

The one question to answer before shopping for your new furnace

Climatecare furnace

  • How long do you plan to stay in your current home? 

Furnaces with higher AFUE ratings require a larger initial investment. If you are just starting out and plan to move to a new, larger, family home in the next 2 or 3 years, a furnace with a super high AFUE rating is probably not the best financial decision.

A high efficiency furnace is rarely a make-or-break factor when selling your house, so it’s not really an investment that will return to you when the house is sold.

However, if you plan to stay in your current family home for the long term, investing in a high efficiency furnace makes the most sense. Here’s how:

*The following numbers are hypothetical. To get a more accurate sense of your savings over time with a high efficiency furnace, give us a call for a quote.

  • A new, TP9C ClimateCare furnace at 98 AFUE might cost $4,000.
  • A new, Carrier Comfort furnace at 80 AFUE could cost $3,400.
  • You pay an extra $600 for the additional AFUE points
  • 18 AFUE points accounts for about 13% greater energy savings
  • Let’s round your heating bills down to $100 per month (you probably spend more, but we’re going to average this out over 12 months of the year for the sake of clarity).
  • 13% of $100 is $13. So each month, with the efficient system, you save $13.
  • You spent $600 more on your 98 AFUE furnace, so we divide that by the $13 you save each month. That equals 46 months.
  • 46 months is about 3.8 years, so it takes you 3.8 years to pay off the difference (through your savings) between the 98 AFUE furnace and the 80AFUE furnace.

So, in this hypothetical scenario, a high efficiency TP9C ClimateCare furnace is the better financial decision if you plan to stay in your home more than 4 years. If you plan to move sooner, the lower efficiency model makes more sense.

To get accurate numbers and timelines, you can price out a few furnace models quickly over the phone with a member of our team.

AFUE rating matters, but the type of fuel and the length of time you plan to live in your current home are also important factors to inform your buying decision.

Get in touch with us to work out the best investment for your family today.