Air conditioning has shifted from a rare luxury to a fairly normal home upgrade in London, as summers have got hotter and prices have come down. Here's what it actually costs to install and run.
London and the South East typically run 20–30% above the rest of the UK for installed systems, mainly reflecting labour costs and access. A single-room system in the room you actually need cool — usually the main bedroom — is the option most homeowners land on before considering whole-home coverage.
British summers are mild by international standards, and most households only run cooling on 10–20 genuinely hot days a year. A typical 2.5kW split system costs roughly £50–£80 a year to run for cooling, or about 18–21p per hour of active use. Modern inverter systems modulate their output rather than running flat out, so cost stays modest even across a hot week. At this level of usage, your overall electricity tariff matters more than the AC unit itself — worth checking you're not overpaying on a standard variable rate regardless.
Most split systems are reversible heat pumps — they can heat as well as cool, and do so efficiently (similar seasonal efficiency to an air source heat pump). Some households use this as supplementary winter heating for one or two rooms rather than running it purely for summer cooling.
Most domestic split system installations are permitted development and don't need planning permission. The exceptions are listed buildings, some conservation areas, and leasehold flats where your freeholder's consent may be required regardless of planning rules — check the borough comparison table and, if you're leasehold, your lease itself before booking an installer — flats have no permitted development rights at all.
Note also that the £2,500 Boiler Upgrade Scheme grant only applies to air-to-air heat pump systems used as your main heating — not to a system installed purely for cooling. The same distinction applies to 0% VAT: it covers an air-to-air heat pump installed as heating, but a standard cooling-only split system doesn't qualify as an energy-saving material under the relief, so expect standard-rate VAT on a pure AC install.
Figures above are 2026 UK averages; your actual quote depends on room size, unit brand, pipe run length and site access.