What Is SEER, and Why Does It Matter in Oklahoma?
A: SEER — Seasonal Energy Efficiency Ratio — measures cooling output against the electricity used to produce it over a season. Higher is more efficient. The important detail in 2026 is that SEER was replaced by SEER2 in 2023. SEER2 tests at higher external static pressure, closer to real duct conditions, so the same physical equipment reads a lower number than it used to. A 15 SEER unit and a 15 SEER2 unit are not the same machine.
Oklahoma's numbers, since the DOE standards took effect on 1 January 2023:
| Equipment | Oklahoma minimum |
|---|---|
| Split-system AC | 14.3 SEER2 / 11.7 EER2 |
| Split-system heat pump | 7.5 HSPF2 |
| Single-package heat pump | 6.7 HSPF2 |
| Gas furnace | 80% AFUE |
Oklahoma is in the DOE South region, so our 14.3 SEER2 floor is higher than the 13.4 SEER2 minimum in the North region. Practically, that means a unit legal to install new in a northern state cannot be installed new here.
More in the SEER glossary entry or on air conditioner installation. Questions: 405-420-4895.