SEER2 explained simply: it’s the seasonal cooling efficiency rating of an AC or heat pump, measured under a tougher test that took effect for equipment made on or after January 1, 2023. Similarly, EER2 rates cooling at a hot 95°F peak, and HSPF2 rates a heat pump’s seasonal heating. In each case, therefore, a higher number means lower energy use.
Information checked on November 4, 2026. The new “2” ratings usually read lower than the old ones for the same equipment, but that doesn’t mean the equipment got worse.
SEER2 explained: what changed in 2023
To begin with, the Department of Energy introduced a new test procedure, called Appendix M1, for equipment manufactured on or after January 1, 2023. Most importantly, it raised the external static pressure used in testing from 0.1–0.2 inches of water to 0.5 inches, according to a NYS Clean Heat fact sheet.
As a result, the new ratings are typically lower. The fact sheet is clear that “the lower values do not imply a change in energy efficiency performance.” In other words, a unit rated 15 SEER under the old test and 14.3 SEER2 under the new one can be the same machine.
- SEER2 (formerly SEER): seasonal cooling efficiency.
- EER2 (formerly EER): peak cooling efficiency at 95°F.
- HSPF2 (formerly HSPF): seasonal heating efficiency of a heat pump, according to the NYS Clean Heat fact sheet.
Converting SEER to SEER2 and HSPF to HSPF2
Unfortunately, there’s no exact formula. In fact, the NYS Clean Heat fact sheet says each heat pump responds differently to the new test, and ducted systems are usually affected more than ductless ones. Still, as a rough guide, Ekotrope says the new cooling rating is about 5% lower than SEER and HSPF2 is about 15% lower than HSPF.
| Old rating | Approximate new rating |
|---|---|
| 14 SEER | About 13.3 SEER2 |
| 15 SEER | About 14.3 SEER2 |
| 16 SEER | About 15.2 SEER2 |
| 8.8 HSPF | About 7.5 HSPF2 |
| 10 HSPF | About 8.5 HSPF2 |
Similarly, the official minimums follow the same pattern. For example, AHRI says the North’s 13.4 minimum is equivalent to the old 14 SEER, and the NY fact sheet lists 15 SEER and 8.8 HSPF as equal to 14.3 SEER2 and 7.5 HSPF2 for split heat pumps.
SEER2 explained by the numbers: minimum ratings
| Equipment | Minimum rating |
|---|---|
| Split central AC, North | 13.4 SEER2 |
| Split central AC, Southeast and Southwest (under 45,000 Btu/h) | 14.3 SEER2 |
| Split central AC, Southeast and Southwest (45,000 Btu/h or more) | 13.8 SEER2 |
| Split heat pump, nationwide | 14.3 SEER2 and 7.5 HSPF2 |
| ENERGY STAR split heat pump | 15.2 SEER2, 11.0 EER2 and 7.8 HSPF2 |
| ENERGY STAR cold-climate ducted heat pump | 15.2 SEER2 and 8.1 HSPF2, plus COP of at least 1.75 at 5°F |
Regional rules apply only to central air conditioners. Also, in the South, AHRI says the standard is based on the installation date rather than the manufacture date. For more detail, see our guide to 14 vs 16 SEER2.
SEER2 explained in dollars: what a higher rating saves
Here’s what the numbers mean in dollars. For this, we used DOE’s typical cooling hours for a 3-ton AC and the August 2026 U.S. average electricity price of 18.16¢ per kWh. Specifically, the formula is 36,000 Btu per hour × cooling hours ÷ SEER2 ÷ 1,000.
| SEER2 | Southeast (3,409 hours) | North (1,705 hours) |
|---|---|---|
| 13.4 | $1,663 a year | $832 a year |
| 14.3 | $1,559 a year | $779 a year |
| 16 | $1,393 a year | $697 a year |
| 18 | $1,238 a year | $619 a year |
So moving from 14.3 to 16 saves about $166 a year in the Southeast but only about $82 in the North. Therefore, a higher rating pays back faster in hot climates. Then compare that saving with the price difference in your quotes, and see our AC replacement cost guide.
HSPF2 explained for heat pumps
Meanwhile, HSPF2 tells you how efficiently a heat pump heats over a season. To compare it with other fuels, though, you can convert it to an approximate COP by dividing by 3.412. For example, the 7.5 HSPF2 minimum works out to a COP of about 2.2, while 10.5 HSPF2 is about 3.1.
However, in cold climates, look beyond HSPF2. ENERGY STAR’s cold-climate label also requires a COP of at least 1.75 at 5°F and at least 70% of rated heating capacity at 5°F compared with 47°F. Also see our guide to the cold-climate heat pump and heat pump vs furnace.
How to use SEER2, EER2 and HSPF2 when you buy
- First of all, check the AHRI certificate for the exact outdoor unit and indoor coil combination, because ratings apply to matched systems.
- Then compare the cooling rating and, if you’re buying a heat pump, HSPF2 for heating.
- In hot, dry areas, also look at EER2, since it rates performance at 95°F.
- After that, check rebate rules. SRP and Columbia, Missouri, for instance, require at least 15.2 SEER2.
- Finally, weigh the yearly savings against the extra cost of the higher-rated model.
SEER2 explained: FAQ
Is SEER2 better than SEER?
Not exactly. It isn’t a better unit; instead, it’s a stricter test. As a result, the same equipment usually scores a bit lower under the new test.
What is a good SEER2 rating?
For example, ENERGY STAR heat pumps need at least 15.2 SEER2. Beyond that, a higher rating mainly pays off in hot climates, as our cost table shows.
Can I still buy a 14 SEER AC?
Yes, in effect, although new equipment carries the new ratings now. In the North, AHRI says the minimum of 13.4 is equivalent to the old 14 SEER.
What’s the difference between EER2 and SEER2?
EER2 measures cooling efficiency at a single hot condition, 95°F, while the seasonal rating averages performance over a cooling season, according to the NYS Clean Heat fact sheet.
Sources and review
Sources: NYS Clean Heat, DOE M1 test procedure fact sheet (January 2024); Ekotrope, the impacts of SEER2 and HSPF2 (updated September 2023); AHRI, 2023 energy efficiency standards; ENERGY STAR, air-source heat pump key product criteria; DOE FEMP, purchasing energy-efficient residential central air conditioners (updated December 2024); EIA, Electric Power Monthly, Table 5.6.A (August 2026 data, preliminary); SRP, air conditioner and heat pump rebates. All checked on November 4, 2026.
Written by: HVAC Switch. Last updated: November 4, 2026. Read our editorial policy to learn how we research prices, or contact us if you spot an error.