What size air conditioner do I need?

Both measure cooling power. 1 kW is about 3,412 BTU per hour, so a 2.5 kW unit is about 8,500 BTU/h.

A unit that is too small runs flat out and still cannot hold the room cool on hot days. A unit that is too big cools in short bursts and switches on and off often, so it removes less moisture and the room can feel clammy. The right size comes from the heat load of the room.

The room size, glass and sun, the roof, insulation, how many people use it, and the equipment and lighting in it, the same points our heat-load assessment covers.

Yes. Most modern split systems are air-to-air heat pumps, so the same indoor unit cools in summer and heats in winter. This calculator sizes for cooling. See our air conditioning and heat pump services.

Every system we install starts with a heat-load assessment of the space: people, lighting, equipment, glazing and opening hours. Talk to us straight away for server or comms rooms, commercial kitchens, rooms that need more than 14 kW, or rooms with more than two ovens, hobs or grills.