Bedroom air conditioning
By Airva Editorial Team · Checked against published UK guidance · Updated
A bedroom is the hardest room in the house to specify air conditioning for, and cooling capacity is not the reason. It is the only room where you lie still, in the dark, for eight hours, with nothing else to listen to. Sound that would disappear under conversation in a living room is conspicuous at two in the morning, and a system that cools beautifully but hums audibly is a system you will end up switching off.
Specify a bedroom on its noise figures and its airflow direction. The cooling looks after itself.
Noise is the specification
Two numbers matter, and only one of them is usually on the brochure front.
The indoor unit's sound pressure at its lowest fan speed. Manufacturers publish figures at several speeds, and the gap is large — the same unit can be around 20 dB(A) on its quiet setting and 40 dB(A) or more on high. Both figures are true. The low-speed one is the bedroom figure, and it is the one to ask for. Under about 25 dB(A) is effectively silent in a quiet room.
Whether it will actually run at that speed. This is where sizing comes in, and it is the part people miss. A correctly sized unit reaches temperature and then cruises on low for hours, which is where the quiet figures live. An undersized unit runs flat out all night. An oversized one is worse in a different way: it cools the room too quickly, shuts off, restarts, and every restart is a burst of fan and compressor noise. Short-cycling is the single most common cause of a bedroom system that nobody likes.
Our quiet air conditioning guide covers what the dB(A) figures mean and which ranges are genuinely quiet.
Where the unit goes matters as much as which unit
A bedroom has one constraint no other room has: someone is lying in a fixed position for hours, and air moving across a sleeping person feels cold well before the room is cold.
- Never blow across the bed. Mount so the airflow crosses the room — over the foot of the bed or along a wall — rather than down onto the pillows. This is the most common bedroom siting mistake and it cannot be fixed with settings.
- High on a wall the bed does not face, with clear space around the unit so the throw is not deflected by a wardrobe.
- Away from the headboard, so the fan is not directly above your head even at low speed.
- Check the condensate route before fixing the position. A bedroom is usually upstairs and often has no convenient drain, so a condensate pump may be needed — around £120–£250, and it has its own faint sound.
Sizing for a sleeping room
Bedrooms are usually smaller loads than the same floor area downstairs, and the peak comes at a different time:
- Fewer occupants and less equipment than a living room or home office.
- The peak is late. A west-facing bedroom absorbs solar gain all afternoon and releases it into the evening — the room is often at its worst just as you go to bed, hours after the sun has moved off it.
- Top floors and loft conversions run hottest, because heat rises and roof gains are large. See our loft conversion guide.
- Night purge helps. If the room can be ventilated when the outside air finally cools, the system has less work to do.
Because the load is modest, most bedrooms are served by a small unit — often 2.0kW to 2.5kW. The temptation to fit something larger "to be safe" is exactly what produces short-cycling and noise.
The winter half
A bedroom unit is a reversible heat pump, and bedrooms are one of the better places to use that. Gentle background warmth on low fan speed, controlled per room, without firing the whole house's heating for one cold bedroom — and at roughly a quarter of the running cost of a plug-in electric heater delivering the same warmth. See heating and cooling.
It also matters for planning: the permitted development right in England is written for heat pumps and excludes equipment used solely for cooling [1], so a reversible unit is the version with planning rights attached.
Outdoor unit siting, and the neighbours
Bedroom systems run at night, which is when neighbours notice things. The outdoor unit position is worth thinking about carefully:
- Away from your own and your neighbours' bedroom windows.
- On anti-vibration mounts, and never on a lightweight structure that can act as a sounding board — a flat roof above a bedroom is a common offender.
- Compliant with the MCS 020(a) sound calculation, which is a condition of permitted development and is assessed at the neighbouring property, not yours [2].
The 2025 removal of the 1m boundary rule means a unit can now sit closer to a fence than it once could, provided the sound calculation supports it [2]. Ask to see that calculation for your actual boundary rather than an assurance that it will be fine.
What a bedroom system costs
| Scope | Indicative installed cost |
|---|---|
| One bedroom, wall-mounted split | £1,500–£3,500 |
| Two bedrooms on a multi-split | £2,800–£4,500 |
| Three to four rooms | £4,500–£8,000 |
Where several bedrooms are involved, a multi-split usually wins — one condenser position, one set of access costs. Note its mode constraint though: every room on the same outdoor unit must be heating or cooling together, which for bedrooms is rarely a problem.
Running cost is low. A bedroom unit through a hot summer is a low tens of pounds at the current Great Britain average unit rate of 26.32p per kWh [3] — the running costs guide works it through.
Frequently asked questions
Is air conditioning too noisy for a bedroom? Not if specified for it. A correctly sized modern unit on low fan speed is around 20 dB(A), which is effectively inaudible. Noise problems in bedrooms almost always come from oversizing, poor mounting or bad airflow direction rather than from the unit itself.
What size unit does a bedroom need? Most bedrooms are served by 2.0–2.5kW, but this must come from a heat-load calculation. Glazing area, orientation and floor level move it more than floor area does.
Where should the indoor unit go? High on a wall, with the airflow crossing the room rather than blowing onto the bed. Airflow across a sleeping person feels cold long before the room does.
What does night mode actually do? Typically it reduces fan speed and allows the set point to drift a degree or two over several hours, matching the body's overnight temperature change. Check the specific unit's behaviour.
Will the outdoor unit disturb neighbours at night? It should not if sited and mounted properly. The MCS 020(a) calculation is assessed at the neighbouring position and is a condition of permitted development [2].
Can it heat the bedroom in winter? Yes, and efficiently — a reversible unit delivers several units of heat per unit of electricity, far cheaper to run than a plug-in heater.
Get a bedroom specified on the right numbers
Tell us about the room — floor, orientation, glazing and where the bed sits — and we will match you with one vetted installer who will size it properly and site it so you can sleep through it: get an installer match.