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Cleveland HVAC Blog

Furnace Efficiency Ratings Don't Tell the Whole Story

Posted by Paul Wadsworth on Tue, Dec 24, 2013 @ 12:03 PM

Furnace efficiency ratings aren’t the last word on how efficiently your new heating system will actually perform. Calculated under standardized laboratory conditions, these ratings may not replicate the circumstances of your home environment. Factors such as a competent installation and available efficiency options also play a role. Like the disclaimer that accompanies miles-per-gallon estimates on a new car, when comparing furnace efficiency ratings, remember, "Your mileage may vary."

energy star guide heater efficiencyThe annual fuel utilization efficiency, or AFUE, is the standard furnace rating prominently displayed on the yellow Energy Guide sticker attached to every new unit. The AFUE figure represents the percentage of heat energy from fuel that actually contributes to heating your home, versus the amount lost in exhausted combustion gases. In a standard efficiency furnace with an 80 AFUE, 20 percent of the fuel's energy is lost and 80 percent is used for heat. Though test results like this in a laboratory setting tell part of the story, these factors also influence real-world AFUE performance:

Proper Installation

About 50 percent of new heating and cooling systems fail to live up to the manufacturer’s efficiency specs because they were not installed correctly.

  • A furnace or A/C installation should always be preceded by a professional load calculation to match the unit’s heating and cooling capacity to the thermal characteristics of the house.
  • Refrigerant charge should be checked and verified before installation and after the unit has been test-run.
  • Airflow through the unit needs top be verified to make sure it is adequate. Often existing duct systems are choked or restricted causing poor performance.


Between 20 and 40 percent of conditioned air is often lost through leaky ducts, potentially offsetting the efficiency gains of a high AFUE furnace. A duct pressurization test can be performed before finalizing furnace installation to pinpoint the location of leaks. This is especially important if ductwork is located in unconditioned crawlspaces or attics!

Efficiency Upgrades

Consider options like variable speed electronically commutated motor (ECM) technology to lower electricity consumption of the furnace blower and boost the AFUE. Variable speed blowers heat and cool more consistently and reduce operating costs.

In Cleveland and surrounding communities, P.K. Wadsworth Heating & Cooling has provided trusted heating and cooling expertise since 1936. Contact us about a more detailed explanation of furnace efficiency ratings before you upgrade your heating system.

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Paul WadsworthPaul Wadsworth is the President and Owner of P.K. Wadsworth Heating and Cooling. For 37 years, Paul has been providing heating and cooling services to the Greater Cleveland area. P.K. Wadsworth has been a trusted Cleveland HVAC service company for over 75 years. The company understand the area's construction and local heating and air conditioning needs. Paul has an MBA from the University of Michigan and a B.S., Industrial Engineering from Purdue University. Paul is the Chairman of COSE's Energy Advisory Council. He's been President of the Cleveland Air Conditioning Contractors of America and a founding member of the local chapter. Paul was born and raised in Cleveland and has been active in the local community. He resides in Cleveland, Ohio with his wife and two sons.

The opinions and statements contained in this article are for general informational purposes only and are not instructions. Only trained, licensed and experienced personnel should attempt installation/repair. The author assumes no liability for the opinions/statements made in this article. Any individual attempting a repair or installation based on this article does so at their own risk of loss.

photo credit: pembina.institute 

Topics: heating system, furnace efficiency ratings, energy efficiency, Energy Guide

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