In shortChoose the system type first, then size it correctly in kW, compare SEER and SCOP efficiency ratings, check indoor noise levels and make sure it has the controls you want. A professional survey ties it all together.
Buying air conditioning for the first time can feel technical. The good news is that a handful of decisions make most of the difference. Work through them in this order.
1. Choose the right type of system
- Wall-mounted split — the most popular choice for a single room.
- Floor console — for loft rooms, conservatories and walls under windows.
- Multi-split — several rooms on one outdoor unit.
- Ducted — concealed, best planned during a renovation.
- Portable units — cheap to buy, but noisy, inefficient and need a window open.
2. Size it correctly in kilowatts (kW)
In the UK, air conditioners are sized by cooling capacity in kW. As a rough guide, a bedroom of up to 15m² needs around 2–2.5kW, a typical double bedroom or office 2.5–3.5kW, and a living room 3.5–5kW. Large glazed areas, south-facing rooms and loft spaces may need more. An undersized unit can’t keep up; an oversized one wastes energy and leaves air feeling damp.
3. Compare efficiency: SEER and SCOP
The energy label shows SEER (seasonal cooling efficiency) and SCOP (seasonal heating efficiency). Higher figures mean lower running costs. Inverter models are far more efficient than fixed-speed ones — see inverter vs non-inverter.
4. Check noise levels
Indoor noise is listed in decibels, dB(A). For bedrooms, look for a low figure on the quietest fan speed and a dedicated sleep mode. Check the outdoor unit’s figure too if it will be near windows or a neighbour.
5. Look at the refrigerant
Most current domestic systems use R32, which has a much lower global warming potential than the older R410A. Systems using R22 are obsolete and can no longer be topped up.
6. Decide on controls and features
Wi-Fi app control, timers, eco modes and air filtration are worth having. Read about smart controls for air conditioning.
7. Budget for professional installation
Split systems must be installed by an engineer qualified to handle refrigerants, and good installation matters as much as the unit. Our installation guide covers typical costs and what affects them.
Choosing an air conditioner: quick answers
What size air conditioner do I need for a bedroom?
Most UK bedrooms need between 2kW and 3.5kW of cooling, depending on size, glazing and whether the room is in the loft.
Which brand of air conditioner is best?
Several established manufacturers make excellent systems. The right model depends on your room, budget and features — installation quality matters as much as the brand.
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