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What CEER measures
CEER stands for combined energy efficiency ratio. The FTC Energy Labeling Rule uses CEER as the energy efficiency descriptor for room air conditioners and portable air conditioners. The federal portable standard also states CEER in Btu per watt-hour. In plain terms, it is a single efficiency number for the unit, not a statement about a single moment of operation.
CEER is not the same as the BTU figure on a listing. BTU describes cooling capacity. CEER describes how much cooling the unit delivers per unit of electricity under the DOE rating method. A unit can have a high BTU figure and a modest CEER, or a lower BTU figure and a higher CEER. The two numbers answer different questions, so read both. For the capacity side, BTU and SACC ratings explained covers the terms.
| Term | What it tells you |
|---|---|
| CEER | Efficiency descriptor for room and portable ACs, stated in Btu per watt-hour |
| BTU | Cooling capacity figure for window units |
| Seasonally adjusted cooling capacity | Department of Energy capacity figure used for portable CEER |
| ENERGY STAR CEER base | Efficiency floor in the ENERGY STAR criteria table for covered classes |
How the rating is set
The U.S. Department of Energy sets energy conservation standards for residential room air conditioners, and manufacturers follow the DOE rating method in 10 CFR 430, Subpart B, Appendix F. The DOE page for consumer room air conditioners describes the product class and points to the standards in 10 CFR 430.32(b). The rating method is the common basis for the CEER figure, so a CEER from one listing can be read next to a CEER from another listing of the same product type.
For portable air conditioners, the federal standard at 10 CFR 430.32(cc) requires a CEER no less than a stated level for single-duct and dual-duct units made on or after January 10, 2025. That section ties the calculation to seasonally adjusted cooling capacity, which is the Department of Energy figure for portables. A portable listing may show a BTU figure and a seasonally adjusted figure; the CEER standard uses the seasonally adjusted one. DOE efficiency standards for room ACs explains the standards side.
What the ENERGY STAR table adds
ENERGY STAR publishes key product criteria for room air conditioners. The criteria page lists CEER base levels by capacity band and by unit style, including units with louvered sides and casement-only or casement-slider window units. Those base levels are the efficiency floor a model must reach for the ENERGY STAR label in the covered classes. The page also notes that the criteria refer to ENERGY STAR Version 5.0 Room Air Conditioners for additional certification details.
The ENERGY STAR room air conditioner overview explains why the number matters: an oversized unit can cool a room before it removes humidity, which can leave the room feeling damp. It also points to variable speed compressor technology as an efficiency feature. CEER is one input to that picture, but it does not replace correct sizing. What ENERGY STAR means for a room air conditioner goes through the label criteria.
Reading the FTC label
The FTC Energy Labeling Rule covers room air conditioners and portable air conditioners. Part 305 includes label content rules for both product types, and the definitions section names CEER as the energy efficiency rating for room and portable air conditioners. One section of Part 305 sets the label content for room and portable air conditioners, so the efficiency figure on that label is CEER.
The label rule does not turn CEER into a room size guide. It is an efficiency disclosure. Use the capacity figure and the maker's stated room size for fit, then use CEER to compare efficiency within the same type and capacity class. Choosing the right BTU for your room size covers the sizing step.
A worked comparison from FEMP
The Federal Energy Management Program gives an example for a room air conditioner without reverse cycle, with louvered sides, in the 8,000 to 13,999 Btu/h range. The example lists CEER 15.4 for the best available model, 14.7 for the ENERGY STAR level, and 10.9 for a less efficient model. Annual energy use in the same example is 584 kWh, 612 kWh, and 826 kWh.
The direction is clear: the higher CEER models use less energy over the stated annual operating profile. That does not mean the highest CEER is automatically the right pick for every room. A small room may need a smaller capacity unit, and a large room may need more capacity. The efficiency number and the capacity number have to be read together. Window AC buying checklist puts the two side by side.
Window versus portable CEER
Window units are room air conditioners: they are compared on their BTU figure for capacity, and their CEER sits on the room air conditioner scale. Portable units are different because the federal standard uses seasonally adjusted cooling capacity in the CEER calculation. When a portable listing has no seasonally adjusted figure, the maker does not list one, and the BTU figure should not be treated as if it were the seasonally adjusted figure.
For a shortlist, compare window units by BTU and CEER within the same capacity band. Compare portables by seasonally adjusted cooling capacity and CEER, and do not mix a portable BTU figure with another portable's seasonally adjusted figure. Portable AC buying checklist covers the portable side, and best portable air conditioners ranks portables on the Department of Energy figure.
Which to choose
| If you | Look for |
|---|---|
| If you are comparing two window units of the same capacity | Compare their CEER figures and read the BTU figure as capacity, not efficiency. Window AC buying checklist |
| If you are comparing portable units | Use seasonally adjusted cooling capacity and CEER; do not compare a BTU figure with another unit's seasonally adjusted figure. Portable AC buying checklist |
| If a listing shows a high BTU figure but a low CEER | Treat the BTU figure as capacity and the CEER as efficiency; the two answer different questions. |
| If you want the ENERGY STAR label | Check the CEER base level for the unit's capacity band and style in the ENERGY STAR criteria table. What ENERGY STAR means for a room air conditioner |
| If you are unsure about room fit | Start with the maker's stated room size and capacity, then use CEER to compare efficiency. Choosing the right BTU for your room size |
Questions people ask
Is a higher CEER always better?
A higher CEER means better efficiency under the DOE rating conditions, but it does not make a unit the right size for a room. Match capacity and stated room size first, then compare CEER within the same type and capacity class.
Does CEER apply to portable air conditioners?
Yes. The FTC Energy Labeling Rule covers portable air conditioners, and the federal portable standard states CEER in Btu per watt-hour using seasonally adjusted cooling capacity. A portable listing may also show a BTU figure, but the CEER standard uses the seasonally adjusted figure.
Where is CEER shown on a room air conditioner?
The FTC label content rules for room and portable air conditioners put CEER in the label information. Maker listings and the ENERGY STAR criteria page also use CEER. Read the label or listing for the unit you are considering.
Is CEER the same as BTU?
No. BTU is a cooling capacity figure. CEER is an efficiency ratio in Btu per watt-hour. A unit can have a high BTU figure and a modest CEER, so read both.
Why does ENERGY STAR mention sizing?
ENERGY STAR notes that an oversized unit can cool a room before it removes humidity, which can leave the room damp. Correct sizing keeps the efficiency number in context. Choosing the right BTU for your room size covers the sizing step.