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What size air conditioner do I need?

A rough guide to sizing air conditioning for a room, and the things that push the size up or down.

Air conditioning is sized by its cooling capacity in kilowatts (kW). Too small and it cannot keep up on hot days. Too large and it switches on and off too often, which wastes energy and wears it out.

A rough guide

Room sizeTypical unit size
Up to about 20 m²2.0 to 2.5 kW
About 20 to 30 m²3.5 kW
About 30 to 45 m²5.0 kW
About 45 to 65 m²7.0 kW
Larger spacesSeveral units, cassettes or a larger system

These are only a starting point for an average room with average glazing and a normal number of people.

What changes the size you need

  • Sun and glazing. South and west facing rooms, big windows and conservatories need more capacity.
  • People. Every person adds heat. Meeting rooms, classrooms, gyms and restaurants need more.
  • Equipment. Computers, servers, ovens, hairdryers and lighting all add heat.
  • Ceiling height and insulation. Tall rooms and poorly insulated buildings need more.

Get it sized properly

We work out the right size at a free survey. Get a quote.

Air conditioning with £0 upfront.

Tell us about the space and get a fixed monthly price. The survey is free and there is no obligation.