Every state in the U.S. has a federally mandated minimum SEER2 rating for new air conditioner and heat pump installations, determined by which of the DOE's three climate regions it falls in. Northern states require a minimum of 13.4 SEER2 for split-system ACs, while Southern and Southwestern states require 14.3 SEER2. Installing a unit below your state's minimum is illegal and can result in fines, void warranties, and disqualify you from rebates.
Find your state below to see the exact minimum SEER2 and HSPF2 requirements for 2026.
Quick Summary: Minimums by Region
Complete State-by-State Requirements
North Region States
These states require a minimum of 13.4 SEER2 for split-system central ACs and 14.3 SEER2 / 7.5 HSPF2 for split-system heat pumps:
South Region States
These states require a minimum of 14.3 SEER2 for split-system central ACs and 15.2 SEER2 / 7.5 HSPF2 for split-system heat pumps:
Southwest Region States
These states also require 14.3 SEER2 for split ACs and 15.2 SEER2 / 7.5 HSPF2 for split heat pumps:
Old SEER Equivalents for Context
If you're comparing these minimums to older equipment rated in SEER:
All regions saw effective increases in minimum efficiency. Even though 13.4 SEER2 looks close to the old 13 SEER minimum, it actually represents roughly 14 SEER in old terms. The DOE raised the real-world bar while switching to the new metric.
Special Cases and Exceptions
State-Level Requirements Above Federal
Some states enforce efficiency requirements above the federal minimum. California has historically been the most aggressive, with its Title 24 building code sometimes requiring higher standards. Check with your state energy office and local building department for any additional requirements beyond federal minimums.
Packaged vs Split Systems
Packaged systems (where the compressor and air handler are in a single outdoor unit) have different minimums than split systems. Packaged ACs have a uniform 13.4 SEER2 minimum regardless of region. This lower minimum reflects the different engineering constraints of packaged systems.
Small-Duct High-Velocity Systems
Small-duct high-velocity (SDHV) systems, such as Unico and SpacePak, have separate (lower) efficiency minimums because their unique design creates inherently higher static pressure. Check AHRI for specific SDHV minimum requirements.
Consequences of Installing Below-Minimum Equipment
Installing a system that doesn't meet your region's minimum SEER2 requirement can result in several problems:
Building inspectors may fail the installation, requiring expensive replacement or retrofit. Manufacturer warranties may be voided if the unit is installed in violation of federal standards. You'll be ineligible for utility rebates, federal tax credits, and many state incentives. Your HVAC contractor may face fines and licensing issues. In some jurisdictions, the homeowner may also be liable.
Verify before you buy. Some online retailers sell equipment without verifying regional compliance. If you purchase a 13.4 SEER2 unit online and live in Florida (which requires 14.3 SEER2), no reputable contractor will install it. Always confirm your region's requirement first.
How This Affects Replacement Decisions
If your current system is 10-15 years old, any replacement in 2026 will be significantly more efficient than what you have, regardless of which region you're in:
Even replacing a code-minimum 13 SEER unit from 2008 with today's code-minimum 13.4 SEER2 delivers a small efficiency improvement plus the benefits of newer technology, better refrigerant, and fresh equipment with a full warranty.
Key Takeaways
- Three DOE regions determine your minimum SEER2: North (13.4), South (14.3), and Southwest (14.3) for split-system ACs
- Heat pumps have higher minimums: 14.3 SEER2 (North) and 15.2 SEER2 (South/Southwest)
- All regions require 7.5 HSPF2 minimum for split-system heat pumps
- These minimums represent a real increase over pre-2023 levels when adjusted for the tougher SEER2 testing
- Some states have additional requirements above federal minimums (check your state energy office)
- Packaged systems have a uniform 13.4 SEER2 minimum nationwide
- Installing below-minimum equipment is illegal and disqualifies you from warranties, rebates, and tax credits
- Any replacement of a 10-15 year old system will provide significant efficiency improvements
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