How much does it cost to run air conditioning?

Running a 2.5kW unit to cool a bedroom typically costs somewhere between 10p and 30p an hour, depending on your electricity tariff and how hard the unit is working. A larger multi-room system costs proportionally more to run, but rarely by as much as people expect, because it’s cooling more space per unit of electricity used, not just using more electricity for the sake of it.

What actually drives the cost

• Your electricity tariff. This is the single biggest factor, and it’s entirely outside the unit itself: the same system costs noticeably different amounts to run on different tariffs.
• The temperature difference you’re asking for. Asking a unit to bring a room down from 30°C to 20°C works it much harder than maintaining 24°C on a warm day. Setting a sensible target temperature, rather than the coldest setting available, makes a real difference.
• How well the room holds temperature. A room that leaks cool air back out through poor insulation or an open door makes the unit run continuously, rather than cycling on and off as it should.
• Efficiency rating. Newer inverter-driven systems (which is what we install) vary their output smoothly rather than switching fully on and off, and use meaningfully less electricity than older, non-inverter units doing the same job.

The heating-mode surprise

Because a reversible system is a heat pump, running it to heat a room in winter is usually cheaper per unit of warmth delivered than a plug-in electric heater, which converts electricity to heat roughly 1-for-1. A heat pump instead moves existing heat from outside air, typically delivering two to four times more heat energy than the electrical energy it consumes. Whether it beats gas central heating on cost depends on your specific gas and electricity prices, and isn’t something we’ll claim either way without knowing your tariffs.

Reducing your running costs without turning it off

• Set a realistic target temperature: 23–24°C in summer, rather than as low as the unit will go.
• Keep doors and windows closed while it’s running, in the same room.
• Use a timer or scheduling feature so it isn’t cooling or heating an empty room.
• Keep the annual service up to date: a dirty filter alone can measurably increase running costs.

If you want a number specific to your home rather than a general range, tell us your typical usage during your quote and we’ll give you a realistic estimate alongside your fixed installation price.