FreeHVACCalculators

AC Electricity Cost Calculator

Work out what an air conditioner costs to run per hour, per month and per cooling season — from its rating or its measured power draw.

Method reviewed October 22, 2026. Version 1.0.0. How it works

Your inputs

Unit system

12,000 BTU/h = 1 ton. Window units are often 5,000–15,000 BTU/h.

Hours the compressor actually runs, not hours the thermostat is set to cool.

US residential average: 18.31¢/kWh (EIA, July 2026). Use the energy charge from your own bill for a better estimate.

Result

Cost per running hour
$0.46
Cost per 30-day month
$110.63
Cost per cooling season
$443

About $0.46 per running hour, or $443 over a 120-day season at 8 h/day.

  • SEER2 is a seasonal average. On the hottest afternoons the unit draws more power than this average; the EER2 option shows that peak.
Cost per day
$3.69
Average power draw
2.52kW
Energy per season
2,417kWh
Show the working
  1. Average power = capacity ÷ SEER2 ÷ 1,000
    36,000 / 14.3 / 1,000 = 2.517 kW
  2. Cost per hour = kW × price
    2.517 × $0.183 = $0.461
  3. Season energy = kW × hours/day × days
    2.517 × 8 × 120 = 2,417 kWh

Three ways to estimate power

  • SEER2 (seasonal): capacity ÷ SEER2 gives the average watts over a cooling season. Best for monthly and seasonal cost.
  • EER2 (peak): capacity ÷ EER2 gives the draw on a hot afternoon. Best for “what does it cost right now?”.
  • Watts: if you have measured the unit with a plug-in meter, or read a clamp meter on the circuit, this is the most accurate input.

Ratings are in BTU per watt-hour, so a 24,000 BTU/h system rated 16 SEER2 averages 24,000 ÷ 16 = 1,500 watts while running.

The number that matters most: run time

Cost scales directly with the hours the compressor actually runs. A thermostat set to cool for 12 hours may run the compressor for 4 on a mild day and 11 in a heat wave. If you have a smart thermostat, its runtime report is the best number to enter.

Use the energy charge from your bill (cents per kWh, including supply and delivery). Fixed monthly charges do not change with use and are not included.

Worked example

These are the example values the calculator opens with, and the result the engine calculates for them.

Inputs

Estimate power from
Capacity and SEER2 rating
Cooling capacity
36,000 BTU/h
SEER2 rating
14.3
Compressor run time per day
8 h
Cooling days per year
120
Electricity price
0.183 $/kWh

Result

Cost per running hour
$0.46
Cost per day
$3.69
Cost per 30-day month
$110.63
Cost per cooling season
$443
Average power draw
2.52 kW
Energy per season
2,417 kWh

About $0.46 per running hour, or $443 over a 120-day season at 8 h/day.

Assumptions

  • Energy = capacity ÷ efficiency × run hours. SEER2 and EER2 are in BTU per watt-hour, so dividing BTU/h by SEER2 gives watts.
  • Fixed monthly charges on your bill are not included — only the per-kWh energy charge.

Limitations

  • Rated efficiency is measured under standard test conditions. Real efficiency depends on installation, airflow, refrigerant charge, duct losses and weather, so bills can differ from this estimate.
  • Run time is the biggest uncertainty. A correctly sized system may run most of the day in a heat wave and very little on mild days.

Frequently asked questions

How much does it cost to run AC for 24 hours?

Enter 24 hours of run time per day to see the cost. In practice a correctly sized system rarely runs continuously except in extreme heat; if yours does on ordinary days, it may be undersized, low on charge, or fighting a duct or airflow problem.

Does a higher SEER2 rating always mean a lower bill?

At the same run time, yes — energy use is inversely proportional to efficiency. Real savings depend on installation quality, airflow, refrigerant charge and duct losses, which ratings do not capture.

What electricity price should I use?

Divide your bill’s total energy charges by the kWh used, or read the per-kWh rate. The default is the latest U.S. residential average published by the EIA at the time of our last update; state averages differ widely.

Sources

  1. Electric Power Monthly, Table 5.6.A — average price to ultimate customers — U.S. Energy Information Administration. U.S. residential electricity price, 18.31 ¢/kWh in July 2026.
  2. 2023 Central Air Conditioner Standards — FAQ — U.S. DOE, Office of Energy Efficiency & Renewable Energy. Regional SEER2 / EER2 / HSPF2 minimum efficiencies effective 2023.

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