Last reviewed: August 2026 · By the HVAC Brief Editorial Team · Our sourcing and editorial standards
Federal minimum efficiency for window and through-the-wall air conditioners rose sharply on May 26, 2026, by between 19% and 50% depending on the equipment class. The standards that had applied since June 1, 2014 were replaced on that date.
The largest jump hits the most common household sizes. A cooling-only louvered unit between 14,000 and 19,900 Btu/h went from a minimum CEER of 10.7 to 16.0, an increase of 50%.
Room air conditioners are regulated separately from central systems, under 10 CFR 430.32(b), and rated on Combined Energy Efficiency Ratio rather than SEER2. The change took effect three months ago and applies to units manufactured from that date, so stock built earlier can still be sold.
The old and new minimums
| Equipment class | CEER before | CEER from May 26, 2026 | Change |
|---|---|---|---|
| Cooling only, with louvered sides , less than 6,000 Btu/h | 11.0 | 13.1 | +19% |
| Cooling only, with louvered sides , of 6,000 to 7,999 Btu/h | 11.0 | 13.7 | +25% |
| Cooling only, with louvered sides , of 8,000 to 13,999 Btu/h | 10.9 | 16.0 | +47% |
| Cooling only, with louvered sides , of 14,000 to 19,999 Btu/h | 10.7 | 16.0 | +50% |
| Cooling only, with louvered sides , of 20,000 Btu/h to 27,999 Btu/h | 9.4 | 13.8 | +47% |
| Cooling only, with louvered sides , of 28,000 Btu/h or more | 9.0 | 13.2 | +47% |
| Cooling only, without louvered sides, , less than 6,000 Btu/h | 10.0 | 12.8 | +28% |
| Cooling only, without louvered sides , of 6,000 to 7,999 Btu/h | 10.0 | 12.8 | +28% |
| Cooling only, without louvered sides , of 8,000 to 10,999 Btu/h | 9.6 | 14.1 | +47% |
| Cooling only, without louvered sides , of 11,000 to 13,999 Btu/h | 9.5 | 13.9 | +46% |
| Cooling only, without louvered sides , of 14,000 to 19,999 Btu/h | 9.3 | 13.7 | +47% |
| Cooling only, without louvered sides , of 20,000 Btu/h or more | 9.4 | 13.8 | +47% |
| Cooling and heating, with louvered sides, , less than 20,000 Btu/h | 9.8 | 14.4 | +47% |
| Cooling and heating, without louvered sides, , less than 14,000 Btu/h | 9.3 | 13.7 | +47% |
| Cooling and heating, with louvered sides, , of 20,000 Btu/h or more | 9.3 | 13.7 | +47% |
| Cooling and heating, without louvered sides, , of 14,000 Btu/h or more | 8.7 | 12.8 | +47% |
Every class rose. Nothing was relaxed. The pattern is that mid-size cooling-only units, which dominate household sales, took the largest increases.
What CEER measures and why it is not SEER2
Combined Energy Efficiency Ratio expresses cooling output against electrical input, including standby power. It is a single-point measure, unlike SEER2, which is a seasonal average across a range of conditions. The two numbers are not interchangeable and a room unit cannot be compared with a central system by putting their ratings side by side.
“Louvered sides” in the equipment classes refers to units with side vents, typical of window installations. Units without louvered sides are generally through-the-wall products, and they carry lower minimums because the installation restricts airflow.
The standard applies at manufacture, not at sale or installation. Units built before May 26, 2026 remain legal to sell and install, so inventory will straddle the two standards for some time. If efficiency matters for a specific purchase, the manufacture date and the CEER on the label decide it, not the year you buy.
Frequently asked questions
Did window air conditioner efficiency standards change in 2026?
Yes. Under 10 CFR 430.32(b), the room air conditioner standards in effect from June 1, 2014 were replaced for products manufactured starting May 26, 2026. Minimum Combined Energy Efficiency Ratio rose across every equipment class, by between 19% and 50% depending on capacity and configuration.
What is the minimum CEER for a window air conditioner?
It depends on capacity and whether the unit has louvered sides and reverse cycle. For cooling-only louvered units manufactured from May 26, 2026, minimums run from 13.1 CEER below 6,000 Btu/h to 16.0 CEER in the 8,000 to 19,900 Btu/h range, per Table 7 to 10 CFR 430.32(b)(2).
What is the difference between CEER and SEER2?
CEER rates room air conditioners at a single operating point and includes standby power. SEER2 rates central air conditioners and heat pumps as a seasonal average across a range of conditions. They are different measures on different equipment and cannot be compared directly.
Can I still buy a window unit built to the old standard?
Yes. The standard applies to units manufactured from May 26, 2026, not to sale or installation. Stock built before that date remains legal to sell. Check the manufacture date and the CEER figure on the label rather than assuming the year of purchase determines the standard.
Methodology and limitations
All figures are quoted from the current text of 10 CFR 430.32(b), Table 6 to paragraph (b)(1) for the standards effective June 1, 2014 to May 26, 2026, and Table 7 to paragraph (b)(2) for products manufactured from May 26, 2026, retrieved from the electronic CFR. Percentage changes are ours, computed class by class.
- These are federal minimums. Many products exceed them and utility programmes may require more.
- Standards attach to manufacture date, not sale or installation date.
- CEER and SEER2 are not comparable measures.
- Nothing here is engineering or purchasing advice for a specific application.
Sources
- US Department of Energy, 10 CFR 430.32(b), room air conditioner standards, Tables 6 and 7.
The HVAC Brief is an independent trade publication. We do not sell equipment, take manufacturer advertising, or accept payment for placement in our research. Corrections welcome.
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