SEER2 standards are the federal minimum efficiency levels that every new residential central air conditioner and heat pump must meet. The U.S. Department of Energy sets them under the Energy Policy and Conservation Act and codifies them at 10 CFR Part 430, Subpart B, Appendix M1. Effective January 1, 2023, the DOE both raised the minimums and changed how efficiency is measured, replacing SEER, EER, and HSPF with SEER2, EER2, and HSPF2. The new metrics come from the Appendix M1 test procedure, which raises the external static pressure used in testing to better reflect how equipment performs in real ducted homes, so a SEER2 number runs a few percent below the old SEER number for the same unit.
The cooling minimums vary by region. In the North, a new split-system central air conditioner must reach at least 13.4 SEER2. In the hotter Southeast and Southwest, split-system air conditioners under 45,000 BTU per hour must reach 14.3 SEER2, and those 45,000 BTU per hour and above must reach 13.8 SEER2. Heat pumps are treated nationally rather than regionally: a split-system heat pump must hit at least 14.3 SEER2 for cooling and 7.5 HSPF2 for heating everywhere in the country. The Southwest layers an additional full-load EER2 requirement on air conditioners to reflect sustained hot-dry operation. These are floors, not targets — utility rebates and the former federal tax credits pointed to far higher tiers.
The 2023 standards are current and stable; they are the baseline a 2026 buyer encounters on every quote. Because they are floors, the more consequential 2026 changes sit above and beside them: the Section 25C and Section 25D federal tax credits that rewarded high-efficiency equipment expired on December 31, 2025, and the EPA's R-454B refrigerant transition governs what refrigerant new equipment uses. The SEER2 minimums themselves did not change in that shuffle. The DOE periodically reviews appliance standards on a statutory cycle, so the minimums can rise again in a future rulemaking, but no higher central-AC or heat-pump minimum has taken effect since January 1, 2023. The regional structure — and the difference between manufacture-date and installation-date enforcement — is detailed under the DOE regional standards.
For a buyer, the SEER2 minimum is the least efficient unit that can legally be installed, not the most cost-effective one. In Arizona and Texas, the federal Southwest and Southeast floor of 14.3 SEER2 for a typical split system is below what utility rebates require — SRP Cool Cash, CPS Energy STEP, and similar programs generally start at SEER2 15 or higher, so a code-minimum unit earns no rebate. Stepping up from the federal floor to a rebate-qualifying tier usually adds equipment cost but unlocks both the rebate and lower operating bills. Compare the SEER2 rating on the AHRI certificate, not the marketing label, and weigh the rebate-qualifying tier against the minimum when sizing the budget.