SEER (Seasonal Energy Efficiency Ratio)
Also known as: SEER2, seasonal energy efficiency ratio
Cooling efficiency rating for air conditioners and heat pumps. Higher SEER = more efficient. Federal minimums in 2026: 14-15 SEER for residential central AC.
SEER measures how efficiently an air conditioner or heat pump cools over a typical cooling season. The number is calculated as cooling output (BTU) divided by electrical energy input (watt-hours), averaged across a range of outdoor temperatures.
Higher SEER means lower energy consumption for the same cooling output. A 20 SEER unit uses roughly 30% less electricity than a 14 SEER unit producing equivalent cooling. The trade-off is purchase price — high-SEER units cost meaningfully more upfront. Federal minimum efficiency standards have stepped up over time; as of 2023, residential central AC must be 14 SEER (15 in southern regions). SEER2, introduced in 2023, uses a slightly different test methodology and produces numbers ~5% lower than legacy SEER for the same equipment. When comparing units, make sure ratings are on the same standard.
Related terms
BTU (British Thermal Unit)
Standard unit of heat energy. One BTU is the energy required to raise one pound of water by one degree Fahrenheit. HVAC equipment is rated in BTU/hour.
Manual J load calculation
ACCA-standard methodology for calculating the heating and cooling load of a building. The required first step before sizing an HVAC system properly.
R-410A vs R-22 refrigerant
R-22 is the legacy ozone-depleting refrigerant phased out under the Montreal Protocol. R-410A is the current standard. R-454B is replacing R-410A starting 2025.