Understanding Furnace and AC Efficiency Ratings

Annual Fuel Utilization Efficiency (AFUE)

AFUE is the efficiency rating for gas and oil-fired furnaces.  This number is given in percentages and tells you how much of your fuel is used to heat the home and how much is wasted.  The minimum industry requirement is 78%, but the consumer can opt to buy a unit with more than 96% efficiency.   Older furnaces have ratings of about 60%, so replacing an old furnace can save you up to 40% on heating bills if you replace it with a high-efficiency unit.  For every $100 you spend running an 80% AFUE furnace, you will spend about $77 to run a 96.6% efficiency furnace.

Heating Seasonal Performance
Factor (HSPF)

HSPF is the measurement used to gauge the efficiency of the heating mode on heat pumps.  Given on a basic number scale, the greater the number, the greater the efficiency and cost-savings.  With a minimum industry requirement of 6.8, units can have ratings up to 9.5.  For every $100 spend running a 6.8 HSPF heat pump, you could spend about $71 running a 9.6 HSPF unit.



Seasonal Energy Efficiency Ratio (SEER)

SEER is the measure of efficiency by which the cooling process of air conditioners and heat pumps is rated.  The numbered scores can reach a maximum of 21; the higher the number, the greater the efficiency and the greater energy savings.  U.S. regulatory agencies require that all new products have a 13.0 SEER rating or better.  For every $100 spent running an 8 SEER air conditioner, you would spend about $61 running a 21 SEER unit.  Please note: in order to reach the high-efficiency ratings, your condensing unit must match the evaporator coil (also known as indoor coil).  If they do not match, the unit will not perform as expected.  If you replace an air conditioner or heat pump system, replace the evaporator coil at the same time to ensure optimal performance.


Energy efficiency

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3500 Newville Rd, Janesville, WI 53545 | Phone: 608-758-9882 | Fax: 608-758-984

Regions Served: Don Martin Heating and Cooling Provides Products and Services To The Following Communities and Counties In Southern Wisconsin and Illinois:

Wisconsin Counties Served Wisconsin Cities Served Illinois Cities Served
Rock County, Wisconsin
Walworth County, Wisconsin
Dane County, Wisconsin
Jefferson County, Wisconsin
Green County, Wisconsin
Janesville, WI
Elkhorn, WI
Delavan, WI
Whitewater, WI
Fort Atkinson, WI
Milton, WI
Edgerton, WI
Macfarland, WI
Madison, WI
Evansville, WI
Orfordville, WI
Darien, WI
Beloit, WI
Lake Geneva, WI
Mukwonago, WI
East Troy, WI
Lake Mills, WI
Brodhead, WI
Monroe, WI
Deerfield, WI
Oregon, WI
Evansville, WI
Albany, WI
Juda, WI
New Glarus, WI
Jefferson, WI
Johnson Creek, WI
Stoughton, WI
Cambridge, WI
Walworth, WI
South Beloit, IL
Rockton, IL
Roscoe, IL
Durand, IL
Harvard, IL
Poplar Grove, IL
Capron, IL
Shirland, IL