Trying to estimate your summer electric bill? This cost of running air conditioner calculator helps you quickly estimate hourly, daily, monthly, and yearly AC electricity costs. It works for window AC units, portable air conditioners, mini-splits, and central AC systems.
Air Conditioner Running Cost Calculator
How the AC cost calculation works
The formula is straightforward:
Cost = (Watts ÷ 1000) × Hours × Days × Electricity Rate × Number of Units
- Watts ÷ 1000 converts power to kilowatts (kW).
- kW × time gives energy use in kilowatt-hours (kWh).
- kWh × utility rate gives your estimated cost.
If you do not know wattage, this calculator can estimate it using Watts = BTU ÷ EER.
Example
Suppose your window AC uses 1,200 watts, runs 8 hours/day, for 30 days/month, and your electricity rate is $0.16/kWh:
- 1,200 W = 1.2 kW
- Daily energy: 1.2 × 8 = 9.6 kWh
- Monthly energy: 9.6 × 30 = 288 kWh
- Monthly cost: 288 × $0.16 = $46.08
Typical air conditioner wattage by type
| AC Type | Typical Capacity | Typical Running Watts |
|---|---|---|
| Small Window AC | 5,000–8,000 BTU | 450–900 W |
| Portable AC | 8,000–14,000 BTU | 900–1,500 W |
| Mini-Split (single zone) | 9,000–24,000 BTU | 500–2,200 W (variable) |
| Central AC | 2–5 tons | 3,000–5,500+ W |
Why your actual AC bill may be different
1) Thermostat setting
Lower setpoints force longer compressor runtime. Even a 1–2°F change can affect energy use.
2) Climate and humidity
Hotter, more humid weather means more work for the AC.
3) Insulation and air leaks
Poor insulation, leaky windows, and unsealed doors increase cooling load.
4) AC efficiency
Higher SEER/EER units usually consume less electricity for the same cooling output.
5) Maintenance condition
Dirty filters, clogged coils, and low refrigerant can make systems run longer and cost more.
How to reduce the cost of running your air conditioner
- Set your thermostat a little higher when you are away.
- Use ceiling fans to improve comfort without lowering thermostat settings.
- Change/clean air filters regularly.
- Seal air leaks and improve insulation.
- Shade windows and close blinds during peak sun hours.
- Schedule annual AC tune-ups.
Frequently asked questions
Is central AC always more expensive than a window unit?
Usually yes in total consumption, because central AC cools a larger area. But on a per-room basis, central systems can be efficient depending on equipment and home design.
Does fan mode use much electricity?
Fan-only mode typically uses much less power than compressor cooling mode, but exact wattage depends on your unit.
Can I use this calculator for mini-splits?
Yes. Enter average running watts (or estimate from BTU and EER) and your daily runtime.
Where do I find my electricity rate?
Check your utility bill for the $/kWh charge. If your utility uses tiered or time-of-use pricing, use your expected average rate.
Estimates only. Actual costs vary by equipment cycling behavior, outdoor temperature, indoor load, and utility billing structure.