SEER2 is the cooling efficiency rating for central air conditioners and heat pumps built since 2023. The minimum you need depends on the type of system and, for central air conditioners, where you live. A split-system central AC under 45,000 Btu/h, a measure of cooling capacity, needs 13.4 SEER2 in northern states and 14.3 SEER2 in the Southeast and Southwest. In Arizona and the rest of the Southwest, the federal rule also sets a minimum for a second rating, EER2 (energy efficiency ratio 2).
What is the difference between SEER and SEER2?
Both ratings measure seasonal cooling efficiency, but they come from different DOE test procedures: Appendix M1, the current test in 10 CFR Part 430, Subpart B, and the older Appendix M. The ENERGY STAR specification defines SEER2 as "the total heat removed from the conditioned space during the annual cooling season, expressed in Btu, divided by the total electrical energy consumed by the air conditioner or heat pump during the same season, expressed in watt-hours." It adds, "The represented value determined in accordance with Appendix M1 is SEER2, and the represented value in accordance with Appendix M is SEER."
Appendix M1 is DOE's current test. The Department of Energy says it uses the industry test standard AHRI 210/240-2024, from the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), the industry's trade association. The test measures SEER2 and HSPF2, the heating efficiency rating for heat pumps.
We found no DOE source that gives a fixed SEER-to-SEER2 conversion. Some groups list their own pairings. NEEP, a regional efficiency organization, treats 14.3 SEER2 as the equivalent of 15 SEER for ducted heat pumps. SRP, a Phoenix-area utility, pairs 16 SEER with 15.2 SEER2, 18 SEER with 17.0 SEER2, and 21 SEER with 20.0 SEER2 in its savings estimate tables. These pairings are each group's own and are not a federal formula.
Federal SEER2 minimums by region
The national minimums apply by manufacture date. Federal rules say central ACs and heat pumps "manufactured on or after January 1, 2023" must meet them. The regional minimums for central air conditioners apply by install date and location. They cover split and single-package ACs "installed on or after January 1, 2023, in the southeast or southwest."
Minimum SEER2 ratings for new central ACs and heat pumps
- Split AC under 45,000 Btu/h, North13.4 SEER2
- Split AC under 45,000 Btu/h, Southeast and Southwest14.3 SEER2
- Split AC 45,000 Btu/h and up, Southeast and Southwest13.8 SEER2
- Split heat pump, all regions14.3 SEER2
- Single-package heat pump, all regions13.4 SEER2
- ENERGY STAR split heat pump (Version 6.2)15.2 SEER2
| Equipment | North | Southeast | Southwest |
|---|---|---|---|
| Split AC under 45,000 Btu/h | 13.4 SEER2 | 14.3 SEER2 | 14.3 SEER2 plus EER2 11.7, or 9.8 at 15.2 SEER2 and up |
| Split AC 45,000 Btu/h and up | 13.4 SEER2 | 13.8 SEER2 | 13.8 SEER2 plus EER2 11.2, or 9.8 at 15.2 SEER2 and up |
| Split heat pump | 14.3 SEER2, 7.5 HSPF2 | Same | Same |
| Single-package heat pump | 13.4 SEER2, 6.7 HSPF2 | Same | Same |
Heat pumps have one national level. The regional table in the federal rule covers only air conditioner classes.
The Southwest EER2 rule
EER2 is a second cooling rating, and the federal rule sets a minimum for it only in the Southwest. The federal rule explains the split for smaller systems: "The 11.7 EER2 standard applies to products with a certified SEER2 less than 15.2. The 9.8 EER2 standard applies to products with a certified SEER2 greater than or equal to 15.2." Larger split ACs use 11.2 EER2 below 15.2 SEER2 and 9.8 EER2 at or above it.
The rule also covers how indoor and outdoor units are paired: "Any model of outdoor unit that has a certified combination with a rating below the applicable standard level(s) for a region cannot be installed in that region."
Which states fall in which SEER2 region
The federal rule defines the two southern regions:
- Southwest: Arizona, California, Nevada and New Mexico.
- Southeast: Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, Puerto Rico, South Carolina, Tennessee, Texas, Virginia, the District of Columbia and the U.S. territories.
Every other state uses the national level. Washington and Ohio appear on the FTC's northern-only label list, so a split AC below the southern minimum can be installed there. Phoenix follows the Southwest rules, and Texas and Florida follow the Southeast rules.
How to read the EnergyGuide label
The FTC says, "The EnergyGuide label lets you know how much energy an appliance uses and see how it compares to the energy use of similar appliances." Central air conditioners and heat pumps carry one.
Under the FTC labeling rule, the label shows SEER2 for cooling. For a split-system AC, it is the lowest rating among all certified indoor and outdoor unit combinations; a split heat pump label shows the low and high ratings. For a heat pump, the label's HSPF2 is calculated for heating Region IV. A cooling-only central AC label also shows a "range of comparability," the lowest and highest SEER2 for all cooling-only central ACs.
A split AC that falls below the southern minimum carries this regional warning: "Federal law allows this unit to be installed only in: AK, CO, CT, ID, IL, IA, IN, KS, MA, ME, MI, MN, MO, MT, ND, NE, NH, NJ, NY, OH, OR, PA, RI, SD, UT, VT, WA, WV, WI, and WY. Federal law prohibits installation of this unit in other states."
How to check the AHRI certificate
For split systems, AHRI says it tests combinations of indoor and outdoor units to verify performance claims. AHRI says consumers should confirm "the indoor and outdoor units are a certified match." To do that, ask your technician for an AHRI Certified Reference Number or an AHRI Certificate of Product Ratings.
AHRI says that for higher efficiency systems, the certificate "may be used to support an application for either a federal tax credit or a rebate or incentive from your local utility or municipality." For the status of the federal credit, see our 25C tax credit guide.
ENERGY STAR SEER2 thresholds
ENERGY STAR Version 6.2 (Rev. March 2025) lists higher levels than the federal minimums. On February 1, 2026, EPA ended the ENERGY STAR specification for central air conditioners, so the split AC level below is the Version 6.2 level that applied before then:
- Split central air conditioners (Version 6.2, before February 1, 2026): at least 15.2 SEER2 and 12.0 EER2.
- Split heat pumps (Version 6.2, Rev. February 2, 2026): at least 15.2 SEER2, 11.0 EER2 and 7.8 HSPF2.
If you are replacing an older system, our guide to the R-410A phase-out covers the refrigerant rules for new installs.