Do Air Conditioners Use a Lot of Electricity?
Published: May 23, 2026
Short answer: an air conditioner uses about as much electricity as a microwave or a small electric heater while it’s running — and the bill depends mostly on how many watts it draws and how long you run it.
How many watts does an air conditioner use?
It varies a lot by type and size:
- Portable, 9,000–14,000 BTU: roughly 1,000–1,800 W
- Window, 5,000–12,000 BTU: roughly 450–1,200 W
- Mini-split, 9,000–12,000 BTU: roughly 700–1,100 W (most efficient)
Two units with the same BTU can use very different amounts of power — that’s what the efficiency rating (EER/SEER) measures.
What that costs
Running cost is simply power × time × electricity price:
Cost per hour = watts ÷ 1000 × price per kWh| Unit | UK @ 24.5p | US @ 16¢ |
|---|---|---|
| 0.5 kW (efficient window) | ~12p/hr | ~8¢/hr |
| 1.0 kW (mid portable) | ~25p/hr | ~16¢/hr |
| 1.5 kW (large portable) | ~37p/hr | ~24¢/hr |
Run a 1 kW unit 8 hours a day and that’s about £2/day in the UK or $1.30/day in the US — roughly £60/month or $39/month of cooling.
How to use less electricity
- Right-size it. An oversized unit wastes power — use our BTU calculator.
- Pick a higher EER/SEER for the same BTU.
- Choose the efficient type — mini-split over window over portable where you can.
- Run it less: timers, sleep mode, and closing curtains on sunny windows.
The simplest way to keep the bill down is to compare units by what they actually cost to run. See every air conditioner ranked by cost per hour, and read our running-cost guide.
