How Much Does a Window AC Cost to Run? (2026 Electricity Data)

A window unit's running cost scales almost linearly with its cooling capacity, because bigger BTU ratings need a bigger compressor that draws more watts. Cooling capacity and wattage are tied together by the unit's efficiency, so a rough rule holds across the size range: every 1,000 BTU adds about 90 to 100 watts of compressor draw. At the April 2026 US average of 18.05¢/kWh from the EIA Electric Power Monthly, here is what each size costs for every hour the compressor actually runs.

5,000 BTU (500W): $0.09 an hour. 6,000 BTU (600W): $0.11. 8,000 BTU (750W): $0.14. 10,000 BTU (900W): $0.16. 12,000 BTU (1,100W): $0.20. 15,000 BTU (1,440W): $0.26.

These are the per-hour numbers while the compressor is on. A 5,000 BTU bedroom unit costs less than a dime an hour. A 15,000 BTU unit sized for an open living-and-kitchen area costs nearly three times that. The size you actually need depends on the room, and oversizing is the most common and most expensive mistake: a unit too big for the space cools fast, shuts off early, and leaves the room cold and damp instead of cool and dry.

The monthly figure depends on two things people usually conflate: how many hours the unit is switched on, and how much of that time the compressor is actually running. Start with the simple version. Run the unit eight hours a night and assume the compressor runs the whole time, and a month of cooling at the US average rate looks like this.

5,000 BTU: $21.66 a month. 6,000 BTU: $25.99. 8,000 BTU: $32.49. 10,000 BTU: $38.99. 12,000 BTU: $47.65. 15,000 BTU: $62.38.

The catch is that a window AC almost never runs at full draw the whole time it is on. The compressor cycles off once the room hits the setpoint and back on when it drifts up a degree or two. In moderate heat, a correctly sized unit runs about 60 percent of the clock. That cuts the real number well below the full-draw figure. The same 8,000 BTU unit that shows $32 on paper actually costs about $19 a month for an overnight bedroom run in 80-degree weather. During a sustained heat wave the compressor runs 85 to 90 percent of the time and the cost climbs back toward the full-draw number, around $28 for that same unit.

Run the representative 8,000 BTU unit eight hours a day for a 30-day month at full draw, which is 180 kWh, and the only thing that changes from one state to the next is the rate. The cost swings by more than three times across the country.

Louisiana (11.9¢/kWh): $21.42 a month. Texas (14.8¢/kWh): $26.64. US average (18.05¢/kWh): $32.49. New York (22.3¢/kWh): $40.14. California (31.4¢/kWh): $56.52. Hawaii (41.2¢/kWh): $74.16.

A renter cooling one bedroom in Baton Rouge and a renter cooling the same bedroom with the same unit in Honolulu are looking at a $53 monthly gap for identical hardware and identical comfort. The state rates guide has the current 2026 number for every state, and the per-state pages run the math at your local rate. Hot, high-rate states like California are where the size and efficiency of the unit start to matter most, because the dollars attached to each extra watt are larger.

For the same room and the same BTU rating, a window unit costs roughly 25 percent less to run than a portable AC. A 10,000 BTU window unit draws about 900 watts. A 10,000 BTU portable draws about 1,200 watts to deliver the same usable cooling. At eight hours a day over a month, that's $38.99 for the window unit against $51.98 for the portable, a gap of about $13 a month or roughly $52 across a four-month cooling season.

The difference is physical, not a brand or a marketing claim. A window unit makes a single insulated penetration through the wall, with the hot side outdoors and the cold side indoors. A portable sits entirely inside the room and vents heat through a hose to the window, which means the unit has to fight the heat leaking back through that hose and the warm air it pulls in to replace what it pushes out. Single-hose portables are the worst offenders. The full breakdown is in the portable AC running cost post, and the window AC calculator will run your specific wattage and rate. If a window is available to mount in, the window unit wins on operating cost every time.

A ceiling fan running eight hours a day costs about $2.60 a month at the US average rate, and a modern DC-motor fan costs closer to $1. The fan does not cool the air. It moves it across your skin, which makes a room feel three to four degrees cooler than the thermostat reads. That perception gap is the lever. The DOE Energy Saver guidance is that running a fan lets you raise the thermostat about four degrees with no loss of comfort, which cuts cooling energy by roughly 12 to 16 percent.

On a window AC that would otherwise cost $38.99 a month, a 14 percent reduction is about $5.46 saved, for a fan that costs $2.60 to run. The fan pays for its own electricity twice over and then keeps saving. The catch most people miss: a fan only helps when someone is in the room to feel it, so leaving it running in an empty room is pure waste. The ceiling fan cost breakdown and the broader summer bill guide cover the rest of the cooling-season levers in dollar terms.

Window AC efficiency is rated in CEER, the Combined Energy Efficiency Ratio, which is the room-AC equivalent of the SEER2 number on a central system. It is just BTU of cooling per watt drawn, so a higher CEER means fewer watts for the same cooling. A 10,000 BTU unit at CEER 11, which is typical for a standard single-stage model, draws about 909 watts. The same capacity at CEER 15, which inverter models reach, draws about 667 watts. That is 27 percent less power for identical cooling, and ENERGY STAR-certified models cluster at the high end of that range per the ENERGY STAR room air conditioner specifications.

In dollars, that 27 percent gap on a $38.99-a-month unit is about $10.50 a month, or roughly $42 across a four-month summer. An inverter window unit like the Midea U cuts runtime wattage about 35 percent against a standard single-stage unit, because instead of slamming the compressor fully on and fully off, it ramps the speed to match the heat load and spends most of its time running slow and quiet. A 15-year-old unit drawing 1,050 watts for the same 10,000 BTU is costing you noticeably more than a new one, and in a high-rate state the replacement can pay back in two to three summers on electricity alone.

A window AC's nameplate watts describe full-tilt operation, which happens only during the hottest stretches. For most of the cooling season the compressor cycles, and the real monthly cost runs 30 to 40 percent below the full-draw figure. The alarming number on the box is the worst case, not the average. A right-sized unit makes that gap work in your favor: it runs longer at a lower draw, holds humidity down, and costs less than an oversized unit that blasts the room cold, shuts off, and short-cycles all night. The appliance wattage chart puts that draw in context against everything else in the house.

The calculator at the window AC page runs this same formula at your state's actual rate and your unit's actual wattage. Read the watts off the label on the side of the unit, enter your daily hours, and it gives you the number for your room instead of the national average.