Portable air conditioner running costs in the UK

What it really costs per hour and per night, by unit size - and the five habits that cut the bill the most.

Cost per hour, by BTU size

Based on the July to September 2026 Ofgem price cap unit rate of ~26p/kWh (26.11p average, paying by direct debit). "Full power" is the compressor running continuously - real use with a thermostat cycles on and off, so expect 50-70% of these figures once the room is at temperature:

*Thermostat cycling in a reasonably insulated room. Your unit's exact draw is on its label (watts) - cost/hour = kW × your unit rate.

What a night's sleep costs

A 9,000 BTU unit cooling a bedroom for 8 hours overnight typically costs £1.05-£1.45. Over a two-week UK heatwave, call it £15-£21 for cool nights - usually money nobody regrets at 3am in July.

Five ways to cut the cost

• Seal the hose gap. A window seal kit stops hot air pouring back in - the single biggest efficiency win.
• Pre-cool, then maintain. Cool the room an hour before bed, then let the thermostat hold it - cheaper than fighting a hot room at midnight.
• Shade the room by day. Curtains/blinds on south-facing glass can halve the heat the unit has to remove.
• Right-size the unit. Undersized runs flat out forever; oversized short-cycles. See the size guide.
• Consider an inverter model if you'll use it every summer - 30-40% less consumption in steady use, and quieter.