Calculators · Cost to run
How much does it cost to run a window air conditioner?
A window AC is far cheaper to run than central air because it cools one room instead of the whole house. A typical mid-size unit draws about 1,000 watts, so running it 8 hours uses roughly 8 kWh. The size you need depends on the room — and oversizing actually wastes money.
per day
$0.75
per month
$22.76
per year
$272.90
A window / room ac uses about 6 kWh a day, costing roughly $0.75/day or $22.76/month at 12.46¢/kWh.
Runs entirely in your browser — nothing you type is sent anywhere. Estimates only; your actual bill depends on your usage and includes delivery charges on top of the supply rate.
What it costs per day, at real rates
Based on a 1,000 W unit running 8 hours (~8 kWh), priced at three of the utilities we track:
| Utility | Rate | Cost per day |
|---|---|---|
| PECO (PA) | 10.789¢/kWh | 86¢ |
| BGE (MD) | 14.609¢/kWh | $1.17 |
| ComEd (IL) | 10.399¢/kWh | 83¢ |
Supply rate only; delivery charges are extra. Use the calculator above for your own utility and usage.
Window AC size by room — and what it draws
| Size | Cools about | Typical draw | 8-hour energy |
|---|---|---|---|
| 5,000 BTU | 100–150 sq ft | ~450 W | ~3.6 kWh |
| 8,000 BTU | 300–350 sq ft | ~715 W | ~5.7 kWh |
| 10,000 BTU | 400–450 sq ft | ~900 W | ~7.2 kWh |
| 12,000 BTU | 450–550 sq ft | ~1,050 W | ~8.4 kWh |
| 15,000 BTU | 550–700 sq ft | ~1,300 W | ~10.4 kWh |
Units cycle with the thermostat, so real energy runs a bit below these full-run figures.
How to cut the cost
- 1
Right-size it — don't oversize
An oversized unit cools fast then short-cycles, which wastes energy and leaves the room clammy. Match the BTU to the room's square footage.
- 2
Buy ENERGY STAR
A certified unit uses noticeably less for the same cooling — worth it if you run it all summer.
- 3
Seal the window gaps
The foam side panels and a bit of weatherstripping stop cooled air leaking out and hot air leaking in — the unit cycles less.
- 4
Use the timer or eco mode
Cooling an empty bedroom all afternoon is pure waste; a timer or the built-in eco/sleep mode cuts runtime.
Common questions
- How much does it cost to run a window AC for 24 hours?
- A 1,000-watt unit running continuously would use about 24 kWh a day, roughly $3 at 13¢/kWh — but because it cycles with the thermostat, real all-day use is usually closer to 12–18 kWh, or about $1.50–$2.50.
- Is it cheaper to run one window AC or central air?
- If you only need one or two rooms cool, a window unit is much cheaper because you're not cooling the whole house. For three or more rooms, central air is usually more efficient overall.
- Can I run a window AC all night cheaply?
- Yes — at typical rates, eight hours of a mid-size unit runs about $1. Use the sleep/eco setting so it eases off once the room is cool.
- What size window AC do I need?
- Roughly 20 BTU per square foot: a 5,000 BTU unit suits a small bedroom (~150 sq ft), 10,000 BTU a large room (~450 sq ft). See the table above.
If the summer bill jumped more than usage explains, your rate may have risen too.