What do all those Energy Efficiency Ratings mean?
The U.S. government requires an efficiency rating for all air conditioning and heating equipment. The rating reflects the percentage of energy used efficiently, with a high rating indicating high-efficiency.
There are three key ratings to consider - SEER, EER, HSPF
EER: - Energy Efficiency Ratio
The ratio of the cooling capacity of the air conditioner in British Thermal Units per hour, to the total electrical input in watts under ARI-specified test conditions. EER is measured at 80 indoor air 95 outdoor air running continuously. EER is measured at one set of conditions.
SEER: - Seasonal Energy Efficiency Ratio
A measure of cooling efficiency for air conditioners and heat pumps. The higher the SEER, the more energy efficient the unit. The government's minimum SEER rating is 13. Analogous to MPG in automobiles. SEER is measured by using the EER above and calculating in a factor for the unit running under a lighter load cycling on and off at 80 indoor and 82 outdoor. SEER is a seasonal average over a specified range of conditions. Since various units don't perform comparably at all temperatures, there will be differences between the single condition EER testing, and the range of conditions SEER testing.
HSPF: - Heating Seasonal Performance Factor
This rating is used in measuring the heating efficiency of a Heat Pump. The higher the number, the more efficient the unit. Analogous to MPG in automobiles. The current industry minimum is 6.80 HSPF.
AFUE: - Annual Fuel Utilization Efficiency
Gas furnaces are rated according to their Annual Fuel Utilization Efficiency. The higher the AFUE rating, the more efficient the unit.