Most efficient · Room Air Conditioners
Most Energy-Efficient Room Air Conditioners in 2026
We ranked 200 ENERGY STAR certified room air conditioners by combined energy efficiency ratio. The K�hl KCVS08B10B comes first: it is listed at 384 kWh a year, about $61.75 to run at the median U.S. state price, EIA July 2026.
Quick answer: the top 3
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Most efficient
K�hl KCVS08B10B
384 kWh/yr · CEER 17 · 8700 BTU/h
$61.75 per year
ENERGY STAR Most Efficient
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Rank 2
K�hl KCVS12B30B
567 kWh/yr · CEER 16.80 · 12700 BTU/h
$91.23 per year
ENERGY STAR Most Efficient
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Rank 3
K�hl KCVS12B10B
569 kWh/yr · CEER 16.20 · 12300 BTU/h
$91.62 per year
ENERGY STAR Most Efficient
A room air conditioner is one of the few appliances where the efficiency rating and the electric bill tell the same story. ENERGY STAR lists every certified unit with its cooling capacity in BTU an hour and its combined energy efficiency ratio, or CEER: the cooling you get for each watt-hour of electricity. A higher CEER means the same cooling for less power, so the list below is ordered by it.
Capacity matters as much as the rating, though. A unit that is too small runs flat out all afternoon, and one that is too large switches on and off and cools the room badly. Use the table to find the most efficient units, then check the capacity column against the size of your room before you compare the yearly cost.
Costs on this page are the ENERGY STAR annual energy figure multiplied by an electricity price. Choose your state or enter the rate from your bill in the calculator, and every row updates. If you already own an air conditioner, add its yearly kWh to see what each model on the list would save you.
Running cost calculator
Prices in the table use the median U.S. state price, EIA July 2026: 16.09 ¢/kWh.
Full replacement calculator with payback time · Cost to run a room air conditioner in every state
How this is calculated
- Yearly cost = the model’s ENERGY STAR annual kWh × your rate. Ten-year cost keeps today’s rate; prices will change.
- Savings = (your current room air conditioner’s yearly kWh − the new one’s) × your rate. Find yours on the yellow EnergyGuide label or measure it with a plug-in meter.
- Statewide averages are not your utility’s tariff. Use the rate on your bill for a closer number.
The 10 most efficient room air conditioners
Showing 10 of 200 ranked models. See all room air conditioners with these filters →
Best in each type
| Type | Top model | kWh/yr | Per year |
|---|---|---|---|
| Window | K�hl KCVS08B10B | 384 | $61.75 |
| Through the Wall | Friedrich WCVT10B10B | 534 | $85.84 |
Models of different types and sizes are not like for like, so each type has its own leader.
Cost of the top 10 per year
All 200 ranked models by annual energy use; the top 10 are highlighted
How we ranked them
Models come from the ENERGY STAR certified room air conditioners list published by the U.S. EPA. We keep only the current listing for each model, and only models that state an annual energy figure. They are ordered by combined energy efficiency ratio (higher is better), a figure ENERGY STAR already adjusts for size, with annual kWh as the tie-break.
Which is calculated with U.S. Department of Energy test procedures for a typical cooling season. Your use will differ with the climate, how many hours a day you cool and the temperature you set. Prices are U.S. EIA statewide residential averages. We do not test products and we do not show retailer prices. See the methodology and data sources.
What to look for in room air conditioners
Read CEER first, capacity second
CEER is cooling output divided by electricity used, so it lets you compare units of different sizes fairly. A bigger unit does not use less energy; it cools a bigger space. Pick the capacity your room needs, then choose the highest CEER at that capacity.
Match the capacity to the room
As a rough guide, about 5,000 BTU an hour suits a room of 100 to 150 square feet, about 8,000 BTU suits 300 to 350 square feet, and about 12,000 BTU suits 450 to 550 square feet. Sun on the room, a kitchen next door or a high ceiling all push the need up. ENERGY STAR publishes a sizing chart if you want the full table.
Small habits that cut the bill
Clean the filter every month in the cooling season, seal gaps around the window frame, and shade the window the sun hits. Setting the thermostat a few degrees higher saves more than any feature, and a timer or sleep mode stops the unit cooling an empty room.
What the K�hl KCVS08B10B costs by state
383.8 kWh a year at each state’s average residential price.
Frequently asked questions
What is the most energy-efficient room air conditioner?
Of the 200 ENERGY STAR certified room air conditioners in our data, the K�hl KCVS08B10B ranks first by combined energy efficiency ratio, with combined energy efficiency ratio of 17 BTU/Wh. It is listed at 383.8 kWh a year.
How much does the most efficient room air conditioner cost to run?
At the median U.S. state price, EIA July 2026 (16.09 cents per kWh), the K�hl KCVS08B10B costs about $61.75 a year, or $5.15 a month. It runs from about $48.82 a year in Louisiana to $184.22 in Hawaii. Enter your own state or rate in the calculator for a closer figure.
How are these room air conditioners ranked?
Models are ordered by combined energy efficiency ratio from the ENERGY STAR certified product list, using only models that list an annual energy figure. Which is calculated with u.s. department of energy test procedures for a typical cooling season. your use will differ with the climate, how many hours a day you cool and the temperature you set. We do not test products and we do not show retail prices.
What does the CEER number mean?
The combined energy efficiency ratio is the cooling output in BTU for each watt-hour of electricity used. This model is listed at 17 BTU/Wh. A higher number means more cooling for the same electricity.
Is it worth replacing an old room air conditioner?
It can be, if the old one uses a lot more electricity. Enter its yearly kWh in the calculator above to see the saving per year and over ten years, or use the room air conditioner replacement calculator for the full comparison.
Does a bigger air conditioner use less energy?
No. A larger unit has more cooling capacity and normally draws more power. What matters is the rating at the capacity you need: choose the unit sized for your room, then pick the one with the highest CEER.
Are window units or portable units more efficient?
Portable units are usually less efficient than window units of similar capacity, because they use warm room air to cool their own parts and then push it outside. This list ranks the ENERGY STAR certified room air conditioners in our data, which is why each model's type is shown.