Most current U.S. mini-split spec sheets now show SEER2, EER2 and HSPF2. Here is what they measure and how to compare them.
On this page
- The 2023 change
- What each rating means
- HSPF2 and climate regions
- Turning HSPF2 into kWh
- Example: one product line
- Federal minimums for comparison
- Converting ratings to something useful
- Why the 12k’s Region IV HSPF2 is lower than the 9k’s and 18k’s
- EER2: the hot-day number
- Where the official numbers live
- FAQ
- Sources
The 2023 change
Since January 1, 2023, U.S. efficiency ratings for newly manufactured residential air conditioners and heat pumps have been expressed as SEER2, EER2 and HSPF2, measured under DOE’s Appendix M1 test procedure (AHRI). AHRI says the M1 test raises external static pressure “by up to five times to reflect field conditions more accurately,” so M1 numbers are generally lower than the old SEER, EER and HSPF values. That higher static pressure applies to ducted systems: Appendix M1 tests non-ducted indoor units, such as wall-mounted mini-split heads, at an external static pressure of zero inches of water (10 CFR 430, Subpart B, Appendix M1); for ductless units, the static-pressure increase doesn’t apply. Either way, you cannot compare an old SEER with a new SEER2 directly.
What each rating means
| Rating | Measures | Units |
|---|---|---|
| SEER2 | Seasonal cooling efficiency | Btu of cooling per watt-hour |
| EER2 | Cooling efficiency at a single hot condition | Btu per watt-hour |
| HSPF2 | Seasonal heating efficiency | Btu of heat per watt-hour |
Higher is better for all three.
HSPF2 and climate regions
Some spec sheets list two HSPF2 values. MRCOOL’s 5th Gen brochure gives HSPF2 for Region IV and Region V; Region V is the colder one and the value is lower. For the 12k model those values are 10.2 and 7.6 (MRCOOL). If you live somewhere cold, the Region V figure is the more relevant one.
Turning HSPF2 into kWh
HSPF2 is the seasonal ratio of total heat output (in Btu) to the total watt-hours of electricity used over the heating season. Electric resistance heat delivers 3,412 Btu per kWh (EIA), which works out to an HSPF of about 3.41. So a unit with HSPF2 7.6 averages roughly 2.2 times as much heat per kWh over the rating season as baseboard heat. Real results vary with your climate and how the unit is installed. Try your numbers in the operating cost calculator.
Example: one product line
| Size (Btu/h) | SEER2 | EER2 | HSPF2 (Region IV) | HSPF2 (Region V) | Line sizes | Factory charge |
|---|---|---|---|---|---|---|
| 9,000 | 23.6 | 14 | 11.5 | 8.6 | see manual | see manual |
| 12,000 (115 V) | 23.5 | 12.5 | 10.2 | 7.6 | 1/4 in + 3/8 in | 30.34 oz |
| 18,000 | 22.5 | 13.7 | 11.5 | 8.5 | 1/4 in + 1/2 in | 44.80 oz |
| 24,000 | 22.7 | 12.7 | 9.5 | 7.1 | 3/8 in + 5/8 in | 67.37 oz |
| 36,000 | 18 | 8.5 | 8.5 | 6.5 | see manual | 109.70 oz |
Source: MRCOOL DIY 5th Gen brochure and the 12k 115 V condenser support page, checked Oct 12, 2026. Confirm against the spec sheet for the exact model number you buy.
Federal minimums for comparison
Since January 1, 2023, DOE’s national minimum for split-system heat pumps is 14.3 SEER2 and 7.5 HSPF2 (split air conditioners have regional cooling minimums instead). Every size in the table above clears both on its SEER2 and Region IV HSPF2 figures. Region IV is the standard rating region; Region V figures are calculated for a colder climate and run lower, so don’t compare them with the 7.5 minimum. [Minimums summarized from DOE’s 2023 standards; check DOE’s current rules for your equipment class.]
Converting ratings to something useful
| From | To | How | Example (MRCOOL 12k) |
|---|---|---|---|
| HSPF2 | Seasonal COP (rough) | HSPF2 ÷ 3.412 | 10.2 ÷ 3.412 ≈ 3.0 (Region IV); 7.6 ÷ 3.412 ≈ 2.2 (Region V) |
| SEER2 | Seasonal cooling COP (rough) | SEER2 ÷ 3.412 | 23.5 ÷ 3.412 ≈ 6.9 |
| Heat needed (Btu) | kWh | Btu ÷ HSPF2 ÷ 1,000 | 20 million Btu ÷ 7.6 ÷ 1,000 ≈ 2,632 kWh |
| Cooling (Btu) | kWh | Btu ÷ SEER2 ÷ 1,000 | 10 million Btu ÷ 23.5 ÷ 1,000 ≈ 426 kWh |
The 3,412 factor is the number of Btu in one kWh (EIA). The cooling row uses an example load.
Why the 12k’s Region IV HSPF2 is lower than the 9k’s and 18k’s
In the table, the 12k (115 V) shows 10.2 Region IV against 11.5 for the 9k and 18k. The brochure doesn’t explain why; a 115 V version of a unit can be built differently from the 230 V units around it. Size the unit with an ACCA Manual J load calculation first; then, among units of the right size, compare HSPF2, and check the AHRI certificate for your exact model number.
EER2: the hot-day number
SEER2 averages over a cooling season; EER2 is measured at a single hot condition. In hot climates where the unit spends long hours at high outdoor temperatures, EER2 tells you more about peak electricity use. Some utility rebate programs set a minimum EER2.
Where the official numbers live
The AHRI Directory lists certified ratings for each matched indoor/outdoor combination (AHRI Directory). Brochure and retail-page numbers should match the certificate; if they don’t, go by the certificate.
FAQ
Is a higher SEER2 always worth it?
Only if you cool a lot. In heating-dominated climates, HSPF2 and low-temperature capacity matter more.
Where do I find official ratings?
On the AHRI certificate for the exact indoor/outdoor combination, and in ENERGY STAR’s product finder.
Sources
- AHRI: https://www.ahrinet.org/2023-energy-efficiency-standards
- MRCOOL: https://doxrepo.mrcool.com/mc-diy-5-br-en-01.pdf
- EIA: https://www.eia.gov/energyexplained/units-and-calculators/british-thermal-units.php
- 12k 115 V condenser support page: https://support.mrcool.com/hc/en-us/articles/35173218846356-DIY-12k-5th-Gen-Condenser-115v
- AHRI Directory: https://www.ahridirectory.org/
- DOE, 10 CFR 430 Subpart B, Appendix M1: https://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-B/appendix-Appendix%20M1%20to%20Subpart%20B%20of%20Part%20430