How much does an air conditioner cost to run?

Cooling capacity is measured in Btu per hour. Electrical consumption is measured in kilowatt-hours. Treating those as interchangeable is the first way an operating-cost estimate goes wrong.

The basic formula

One kilowatt equals 1,000 watts. One kilowatt-hour is one kilowatt used for one hour.

Energy in kWh = watts ÷ 1,000 × operating hours

Cost = energy in kWh × electricity rate in dollars per kWh

A 1,000-watt appliance drawing that power for eight hours uses 8 kWh. At $0.20/kWh, that costs $1.60.

Account for compressor cycling

An AC compressor does not necessarily draw its rated running power for every clock hour. Conventional units cycle, while variable-speed systems modulate. A rough estimate can include a duty-cycle fraction:

Monthly cost = kW × hours/day × days × duty cycle × $/kWh

At 1 kW, eight hours per day, 30 days, 70% average duty, and $0.20/kWh:

1 × 8 × 30 × 0.70 × $0.20 = $33.60 per month

The 70% figure is an assumption, not a fact about every unit. Weather, thermostat setting, room load, sizing, and control behavior change it.

Use your rate, not a generic national number

Find the marginal energy rate on your utility tariff or bill. Include time-of-use pricing when relevant. Dividing the entire bill by kWh can blend fixed customer charges with energy charges and may not represent the cost of one additional kWh.

State and national EIA averages are useful for broad comparisons, not personal bill predictions.

Nameplate, EnergyGuide, or measured energy?

• Nameplate or specification watts can support a high-level estimate, but all-hours multiplication may overstate cycling equipment.
• EnergyGuide annual cost provides a standardized comparison under federal assumptions. It is not your climate or schedule.
• Measured kWh over representative weather gives the best household-specific evidence when measured safely with suitable equipment.

Include fan-only and standby consumption when precision matters.

Capacity does not reveal input power by itself

Two units with the same cooling capacity can use different electrical power. Efficiency metrics connect standardized cooling and energy performance, but actual input still varies with conditions and operating mode.

Do not divide a headline BTU figure by an unrelated efficiency number and present the result as guaranteed running watts. Use the current model’s EnergyGuide and specification data.

Try our electricity-cost calculator with your own wattage and rate. Run a low, middle, and high duty-cycle scenario rather than trusting one deceptively precise result.