Window air conditioners ranked by cost to run
Window-mounted units that sit in a sash or wall opening — efficient and popular in the USA. Ranked by real running cost per hour.
- Typical efficiency
- EER ~10.5
- Power (12k BTU)
- ~1,140 W
- Cost/hr (UK)
- ~£0.28
- Install
- DIY into a window
- Noise
- 50–60 dB
Typical figures for a 12,000 BTU unit at UK rates (£0.245/kWh) — see the live listings below for exact specs per model.
Guides for window air conditioners
Window air conditioners: frequently asked questions
How much does a window air conditioner cost to run?
Window units average an EER around 10.5 — more efficient than portables. A 10,000 BTU model draws about 950 W, roughly $0.15 per hour at the US average of $0.16/kWh (about £0.23 per hour at UK rates). Larger 14,000–18,000 BTU units cost proportionally more.
Are window air conditioners cheaper to run than portables?
Generally yes. For the same BTU, a window unit’s higher EER (~10.5 vs ~8.5) means roughly 15–25% lower running cost per hour, because it vents heat directly outside instead of through a hose.
Why are window air conditioners rare in the UK?
Most UK windows open outward (casement) rather than sliding up (sash), so US-style window units do not fit. That is why UK results here are dominated by portables and mini-splits, while window units are far more common in the USA.
