Air conditioners can be a major part of a household’s summer electricity use. This guide shows how to estimate their energy cost using input watts, running time and your utility rate.
Updated October 20, 2026. The examples below are calculations, not measurements of specific products.
1. Cooling capacity is not electrical input
BTU per hour measures cooling output, while watts measure electrical input. Two units with the same cooling capacity can use different amounts of electricity. Window, portable, central and inverter systems also behave differently. Read the input-power label or manufacturer specifications rather than converting BTU directly into watts.
For illustration, the table below uses 500W, 800W, 1,200W and 3,200W. These are assumed inputs, not guaranteed wattages for a given BTU rating. Room size, insulation, humidity, outdoor temperature and equipment efficiency affect actual use.
2. Calculate electricity use and cost
Daily kWh = input watts × operating hours × assumed duty cycle ÷ 1,000
Daily cost = daily kWh × electricity rate in dollars per kWh
A duty cycle of 0.7 means the compressor runs at the assumed power for 70% of the time. It is an example assumption, not a typical value that applies to every AC. Variable-speed units can change their power continuously. If you have measured average watts over the full operating period, use those watts without applying another duty-cycle discount. Fan and standby use may add energy.
All examples use 16.8¢/kWh ($0.168/kWh) as an illustrative rate, not a claim about the current U.S. average. Enter your own tariff from your electricity bill. The EIA electricity price table provides dated state and national comparisons.
3. Worked cost comparison
Assumptions: 8 operating hours per day, 70% duty cycle, 30 days and $0.168/kWh. Calculations use unrounded energy values; displayed costs are rounded to cents.
| Assumed input | Daily kWh | Daily cost | 30-day cost |
|---|---|---|---|
| 500W | 2.80 | $0.47 | $14.11 |
| 800W | 4.48 | $0.75 | $22.58 |
| 1,200W | 6.72 | $1.13 | $33.87 |
| 3,200W | 17.92 | $3.01 | $90.32 |
For example: 800 × 8 × 0.7 ÷ 1,000 = 4.48 kWh per day. Then 4.48 × $0.168 × 30 = $22.5792, rounded to $22.58. At $0.30/kWh the same use costs $40.32 over 30 days. Fixed customer charges, taxes, demand charges and tiered or time-of-use pricing are excluded.
4. Reduce avoidable cooling use
- Check and clean or replace filters according to the manufacturer’s schedule.
- Use ceiling fans for comfort while a room is occupied; switch them off when leaving.
- Seal gaps around window units without blocking required ventilation or drainage.
- Choose a comfortable thermostat setting and adjust it when away, taking account of occupants’ health, humidity and pets.
See the U.S. Department of Energy home cooling guide for cooling and efficiency guidance.
Calculate your cooling costs
Use the Appliance Electricity Cost Calculator with your own input watts and electricity rate. For this table’s 70% assumption, enter 5.6 equivalent full-power hours (8 × 0.7). Actual measured consumption is preferable where available.
Related guide: Space heater electricity use and cost.