What Does It Cost to Run an Air Conditioner?
A 12,000 BTU air conditioner (about 3.5 kW of cooling) with an energy efficiency ratio of 11 draws about 1,100 watts. Run for 8 hours a day over a 90 day summer, with the compressor on 70% of the time, it uses 554 kWh, which costs about $101 at the US average of 18.16 cents per kWh.
Try your own numbers
Last checked 11/10/2026. Sources: U.S. Department of Energy: Estimating appliance and home electronic energy use; Virginia Cooperative Extension: Estimating Appliance and Home Electronic Energy Use (typical wattages, 2020); U.S. Energy Information Administration: Electric Power Monthly, Table 5.6.A.
How these figures are checked. Sourced figures link to the publisher’s own page and carry a last-checked date; our own rules of thumb are labelled as such. Run by JB, an independent publisher based in Australia. Spotted a mistake? Email hello@calcfig.com.
How the cost of air conditioning is worked out
An air conditioner is rated by the cooling it delivers (BTU per hour, or kilowatts) and by how efficiently it turns electricity into that cooling. The electricity it draws is the cooling divided by the efficiency. 12,000 BTU per hour is about 3.5 kW of cooling; at an energy efficiency ratio (EER) of 11, the unit draws 12,000 ÷ 11 = about 1,100 W. The EER of 11 is an assumption for the example, not a measured figure for any model: your unit’s label or specification sheet gives its real power draw.
1,100 W for 8 hours is 8.8 kWh at full power. A compressor does not run flat out all day, so the example assumes it is on 70% of the time: 6.16 kWh a day. Over 90 days that is 554 kWh, and at 18.16 cents per kWh the season costs $100.68, or about $1.12 a day. Change the hours, the days and the duty to match your home, and pick your state, because its electricity price may be very different from the national average.
Bigger rooms, hotter days, poor insulation and a dirty filter all push the duty cycle up. A hot spell can use far more than this estimate; a mild summer far less.
Common questions
How many watts does an air conditioner use?
It depends on its size and efficiency. A 12,000 BTU unit with an EER of 11 draws about 1,100 W while the compressor runs. Check the label on your own unit.
Does the compressor run all the time?
No. It cycles on and off to hold the temperature. The calculator lets you set the share of time at full power; 70% is an example, not a rule.
Is it cheaper to leave it running all day?
Usually not. Cooling an empty house costs electricity, and the unit has to work harder to catch up later only if the home has warmed a lot. The figures here let you compare different hours.