SEER
Seasonal Energy Efficiency Ratio: total cooling output over a cooling season divided by electricity used, in BTU/Wh (US) or W/W (EU).
SEER measures the seasonal cooling efficiency of air conditioners and heat pumps. Two incompatible definitions exist, so units must be checked:
- US (AHRI 210/240): BTU of cooling per watt-hour of electricity. Since 2023 the test procedure changed to SEER2, with higher external static pressure; SEER2 values are about 4–5% lower than old SEER for the same unit.
- EU (EN 14825): dimensionless W/W ratio, weighted over a standard cooling season.
1 W = 3.412 BTU/h, so SEER (W/W) = SEER (BTU/Wh) / 3.412
Example: SEER 16 BTU/Wh ≈ 4.7 W/W
EER is the equivalent at one test point (95 °F / 35 °C outdoors)
US federal minimums since 2023 are 13.4 SEER2 in northern states and 14.3 SEER2 in the southern region for split systems; high-end inverter units exceed 20–25. In the EU, an A+++ cooling label requires SEER of at least 8.5 W/W, and good inverter splits reach 6–9.
Annual cooling electricity can be estimated from seasonal cooling load divided by SEER, with load scaling roughly with cooling degree days. The heating counterparts are SCOP (EU) and HSPF (US).
Related terms
All terms →- SCOP (Seasonal COP)
A heat pump's average coefficient of performance over a standardised heating season, weighting test points by how often each outdoor temperature occurs.
- COP (Coefficient of Performance)
The ratio of useful heat (or cooling) delivered by a heat pump to the electrical energy it consumes, measured at a specific operating point.
- Cooling degree days (CDD)
A measure of how much and for how long outdoor temperature exceeds a base temperature, used to estimate air-conditioning demand.
- Heat pump
A device that uses a refrigeration cycle to move heat from a cooler source (air, ground, water) to a warmer sink, delivering 2–5 units of heat per unit of electricity.
- BTU (British thermal unit)
A traditional unit of heat, approximately the energy needed to raise one pound of water by one degree Fahrenheit; 1 BTU (IT) = 1,055.06 J.