Central Air Conditioner Running Cost Calculator
Enter your system's size in tons and its SEER2 rating, add the hours the compressor runs, and get the cost per hour, day and month in your state.
Central air cost
A04Scenario A
Sets the electricity rate. Pick US average if you're not sure.
From EIA for US average. Use the rate on your bill if you know it.
Rate used: 18.4¢/kWh · US average · EIA reference 2025–26 (data as of 2026-09-26) ·
1 ton = 12,000 BTU/h. The model number usually contains the size: 24 = 2 tons, 36 = 3 tons, 48 = 4 tons.
On the outdoor unit's EnergyGuide label or the AHRI certificate.
Estimated cost per month
- Running watts (tons × 12,000 ÷ SEER2)2,571 W
Per year assumes the same use every day.
Estimate. Formula and sources are under “How it works”. Change any input; the result updates as you type.
2026 note: The federal 25C and 25D tax credits ended for installations after Dec 31, 2025. Our numbers use 2026 rules. State rebates, HEAR/HOMES programs and utility programs may still apply.
Formula
How it works
- Watts while running = tons × 12,000 ÷ SEER2
- kWh per day = watts ÷ 1,000 × compressor hours
- Cost per hour = watts ÷ 1,000 × rate
- Cost per month = kWh per day × days × rate
SEER2 is seasonal BTU of cooling per watt-hour, so capacity divided by SEER2 gives the average power draw while the compressor runs. A 3-ton system at SEER2 14 draws about 2,570 W; at SEER2 16, about 2,250 W. How many hours it runs depends on your climate and thermostat. Hot states have more cooling degree-days and longer run times.
Sources: SEER2 definition, AHRI Standard 210/240-2023. Electricity rate: EIA Electric Power Monthly table 5.6.A.
Worked example
A worked example
A 4-ton system with a SEER2 of 16 draws 4 × 12,000 ÷ 16 = 3,000 W while the compressor runs. Ten hours a day is 30.00 kWh. At the Texas rate of 15.5¢/kWh that's $0.46 an hour, $4.65 a day and $144.15 for a 31-day month.
Reference
Reference table
Central air cost per month at 18.4¢/kWh (US average), 8 compressor hours a day
| SEER2 14 | SEER2 16 | SEER2 18 | SEER2 20 | |
|---|---|---|---|---|
| 2 tons | $75.70 | $66.24 | $58.88 | $52.99 |
| 3 tons | $113.55 | $99.36 | $88.32 | $79.49 |
| 4 tons | $151.41 | $132.48 | $117.76 | $105.98 |
| 5 tons | $189.26 | $165.60 | $147.20 | $132.48 |
Questions
FAQ
How much does it cost to run central air all day?
If the compressor ran all 24 hours, a 3-ton SEER2 14 system would use about 61.7 kWh, an estimated $11.36 a day at the US average rate of 18.4¢/kWh. A system that runs nonstop on a mild day is usually undersized, low on refrigerant or leaking air through the ducts.
What's the cost difference between a 3-ton and a 4-ton system?
At the same SEER2 of 14, a 4-ton system draws about 3,430 W versus 2,570 W for a 3-ton, a third more per hour. A properly sized larger system also cools faster, so the monthly gap is usually smaller than the hourly one. Use Compare mode with your real run hours.
How much does SEER2 16 save over SEER2 14?
For a 3-ton system running 8 hours a day at the US average rate, SEER2 14 costs an estimated $113.55 a month and SEER2 16 about $99.36, a difference of about $14 a month in cooling season. The gap grows with higher rates and longer seasons.
How much does central air cost per month in Arizona?
A 5-ton, SEER2 14 system running 12 hours a day at Arizona's rate of 15.0¢/kWh comes to an estimated $231.43 a month. Pick your state above for your own number.
Why is my real AC cost different from this estimate?
The calculator uses the rated efficiency and the hours you enter. Real run time changes with the weather, the thermostat setting, insulation and duct leaks, and your bill adds fixed charges and time-of-use pricing.
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