How to use the AC Electricity Cost Calculator
Start with the air conditioner input power in watts if you know it. This is the most direct way to estimate electricity use. If you only know cooling capacity, switch to BTU + EER mode and the calculator will estimate input watts from the efficiency rating.
Enter your daily use, compressor run time, electricity price, cooling days per month, and cooling months per year. The duty cycle matters because most air conditioners do not run the compressor at full rated power every minute they are turned on.
If you are still choosing a properly sized unit, start with the AC BTU Calculator. If you already know the capacity and want to check room coverage, use the AC Room Size Calculator.
AC electricity cost formula
input watts = known watts, or cooling capacity BTU/h / EER or SEERaverage running watts = input watts x duty cycle %daily kWh = average running watts x hours per day / 1000monthly kWh = daily kWh x cooling days per monthcooling season cost = monthly kWh x electricity price x cooling months per yearThe formula estimates energy use during active cooling months. It is different from a whole-home utility bill because it does not include other appliances, utility fees, taxes, or time-of-use pricing.
Assumptions and methodology
This calculator focuses on electricity use, not cooling capacity sizing. It separates rated input power from average running power because air conditioners cycle on and off, and inverter models may modulate output instead of using one fixed wattage.
- Known watts is the best input if you have a label, spec sheet, smart plug, or energy meter reading.
- BTU + EER mode estimates input watts by dividing cooling capacity by EER or SEER.
- Duty cycle reduces rated input watts to an average running power estimate.
- Cooling season cost uses cooling days per month and cooling months per year, so it can model seasonal use instead of all 12 months automatically.
Example calculations
1,200 W AC, 8 hours per day
A 1200 W air conditioner used for 8 hours per day at a 60% duty cycle uses about 5.76 kWh per day. At $0.18/kWh, that is about $31.10 per active month.
If the same unit ran at full rated power for the same hours, it would cost about $51.84 per active month. That comparison shows why compressor run time is one of the most important assumptions in an AC electricity cost estimate.
AC electricity cost chart
This chart estimates input watts from BTU/h using an EER of 10, then assumes 8 hours/day, 60% duty cycle, 30 cooling days per month,4 cooling months per year, and $0.18/kWh electricity.
| AC capacity | Input watts | Daily energy | Monthly cost | Season cost |
|---|---|---|---|---|
| 8,000 BTU/h | 800 W | 3.84 kWh | $20.74 | $82.94 |
| 12,000 BTU/h | 1200 W | 5.76 kWh | $31.10 | $124 |
| 18,000 BTU/h | 1800 W | 8.64 kWh | $46.66 | $187 |
| 24,000 BTU/h | 2400 W | 11.52 kWh | $62.21 | $249 |
Related calculators
TV Electricity Cost Calculator
Estimate TV electricity use and running cost from watts, hours, electricity price, and standby power.
AC BTU Calculator
Estimate air conditioner cooling capacity from room size, ceiling height, sun, insulation, climate, people, and heat load.
AC Room Size Calculator
Estimate what room size an air conditioner can cool based on BTU or kW capacity.
AC Running Cost Calculator
Estimate hourly, nightly, weekly, monthly, and seasonal air conditioner running cost.
FAQ
How much does it cost to run an air conditioner?
Using the default example of 1200 W, 8 hours/day, 60% duty cycle, and $0.18/kWh, this AC Electricity Cost Calculator estimates about $31.10 per active month and $124 for a 4-month cooling season.
How do I calculate AC electricity cost?
Multiply input watts by hours of use and duty cycle, divide by 1000 to get kWh, then multiply by your electricity price per kWh. For monthly cost, multiply daily kWh by cooling days per month.
Is AC BTU the same as watts?
No. BTU/h describes cooling capacity, while watts describe electrical input power. A 12,000 BTU/h air conditioner does not use 12,000 watts. If you only know BTU/h, use EER or SEER to estimate input watts.
What duty cycle should I use for an air conditioner?
Use 100% for a conservative maximum-cost estimate. For typical cycling use, 50-70% is often a practical planning range, but real duty cycle depends on weather, thermostat setting, room size, insulation, humidity, and whether the unit is inverter-driven.
How do EER and SEER estimate AC power use?
EER and SEER are efficiency ratings in BTU per watt-hour. A rough input power estimate is watts = cooling capacity BTU/h divided by EER or SEER. Actual power can differ because SEER is seasonal and real conditions vary.
Why is my actual AC bill different from the calculator?
Actual cost can differ because electricity rates, time-of-use pricing, taxes, outdoor temperature, thermostat setting, humidity, maintenance, room insulation, and compressor cycling all affect real energy use.