Since January 1, 2023, air conditioners and heat pumps sold in the US are rated with SEER2, EER2 and HSPF2 instead of SEER, EER and HSPF. The equipment did not suddenly become less efficient. The test changed to reflect real homes more closely, mainly by assuming more resistance from ductwork, and the numbers came out lower.
What SEER2 measures
SEER2 (Seasonal Energy Efficiency Ratio 2) is the cooling delivered over a typical season, in BTU, divided by the electricity used, in watt-hours. A higher number means lower cooling bills. A 16 SEER2 system uses about 20% less electricity for cooling than a 13.4 SEER2 system of the same size.
What HSPF2 measures
HSPF2 (Heating Seasonal Performance Factor 2) is the heating equivalent for heat pumps: BTU of heat delivered over a heating season per watt-hour of electricity. Divide HSPF2 by 3.412 to get an approximate seasonal COP. An HSPF2 of 8.5 means the heat pump delivers about 2.5 times as much heat as electric resistance heating for the same electricity.
What EER2 measures
EER2 is efficiency at a single hot condition (95°F outside). It matters most in very hot, dry climates where the system spends many hours at full load.
Converting old ratings
| Old rating | Approximate new rating |
|---|---|
| SEER 14 | 13.4 SEER2 |
| SEER 15 | 14.3 SEER2 |
| SEER 16 | 15.2 SEER2 |
| SEER 18 | 17.1 SEER2 |
| SEER 20 | 19 SEER2 |
| HSPF 8.8 | 7.5 HSPF2 |
| HSPF 9 | 7.7 HSPF2 |
| HSPF 10 | 8.5 HSPF2 |
Rough rule: SEER2 ≈ SEER × 0.95, and HSPF2 ≈ HSPF × 0.85.
Current federal minimums
| Equipment | North | South and Southwest |
|---|---|---|
| Central air conditioner (split) | 13.4 SEER2 | 14.3 SEER2 (plus EER2 minimums in the Southwest) |
| Heat pump (split) | 14.3 SEER2 and 7.5 HSPF2 | 14.3 SEER2 and 7.5 HSPF2 |
Which rating is worth paying for?
- Hot climates (lots of cooling): pay for SEER2 and EER2. Going from the minimum to 16–17 SEER2 usually pays back.
- Cold climates (lots of heating): HSPF2 matters more than SEER2. Look for 8.5+ HSPF2 and, just as important, the capacity and COP at 5°F. See cold-climate heat pumps.
- Mild climates: the difference between 15 and 20 SEER2 is often only $50–$100 a year. Spend the money on ductwork and insulation instead.
Calculate your own savings with the SEER2 savings calculator.
Check the matched rating
SEER2 and HSPF2 apply to a matched outdoor unit, indoor coil or air handler, and sometimes furnace. The same outdoor unit can have a different rating with a different indoor coil. Ask for the AHRI certificate number of the exact combination on your quote.