Home office
air conditioning
A home office is a small room with a person and several hundred watts of electronics in it, occupied for eight hours at exactly the time of day the sun is on the building. It needs more cooling than its floor area suggests and it needs to be quiet enough to take a call in.
- Free survey and a fixed written price
- Sized from a calculation, not from the floor area
- One day on site for most single rooms
Brands we work with
A home office needs about 12 percent more cooling than a bedroom of the same size, because of the equipment and the occupant. A typical 10 to 12 square metre office needs 2.0 to 2.5kW and costs 1,750 to 2,400 pounds fitted.
Running it through a working day costs roughly 12 to 22 pence an hour at current rates, which is less than most people assume and less than a fan heater in winter.
What size a home office needs
Using the same model as the sizing calculator on this site, with the 12 percent uplift for office use applied on top of aspect, floor and glazing.
| Room | How it works out | Unit |
|---|---|---|
| Box room office, 8 m², north facing | 8 × 0.14 = 1.12, less 10% aspect, plus 12% use | 2.0kW |
| Small office, 10 m², east facing | 10 × 0.14 = 1.40, plus 12% use | 2.0kW |
| Office, 12 m², south facing, first floor | 1.68, plus 18% aspect, 5% floor, 12% use | 2.5kW |
| Garden room office, 14 m², large glazing | 1.96, plus 18% glazing, 12% use | 2.5kW |
| Loft office, 14 m², west facing | 1.96, plus 18% aspect, 30% loft, 12% use | 3.5kW |
The equipment load, which is bigger than it looks
Nearly all the electricity that goes into a computer comes back out as heat. A laptop with a dock and two monitors is commonly 100 to 150W continuous, a desktop with a graphics card can be several hundred, and a person adds around another 100W.
In a large room that is negligible. In a nine square metre box room with the door shut it is the dominant load in the morning before the sun reaches the window, which is why home offices get uncomfortable earlier in the day than the rest of the house.
It is also why an office is a room where the calculation is worth doing rather than assuming a small room needs a small unit.
Quiet enough for a call
The number to ask for is sound pressure at the lowest fan speed. The best wall units are 19 dB(A) and most good ones are between 19 and 24, which is below the noise floor of a typical room and will not reach a microphone.
What does reach a microphone is a unit that keeps starting and stopping, and that is an oversizing problem rather than a model problem. A correctly sized unit settles into a continuous low output and stays there.
Position helps too. A unit discharging across the room rather than down onto the desk keeps both the air movement and the noise away from where you are sitting.
What it actually costs to run a working day
A 2.5kW unit holding a small office at temperature does not draw 2.5kW. Once the room is down to temperature an inverter unit modulates to whatever the room is losing, which for a small internal office is commonly 300 to 600W.
At current electricity rates that is roughly 12 to 22 pence an hour, so a full working day is usually under two pounds and often well under. There is a calculator that uses your own tariff on the running costs page.
In winter the same unit heats the office for less than a plug-in heater costs, which for a room the central heating reaches badly is often the bigger saving.
What it costs
| Scope | System | Installed price |
|---|---|---|
| Box room or small office | 2.0kW wall unit | £1,750 to £2,300 |
| Standard home office | 2.5kW wall unit | £1,900 to £2,700 |
| Loft or garden room office | 3.5kW wall unit | £2,300 to £3,000 |
| Office plus one bedroom | 2 unit multi-split | £3,200 to £4,400 |
| Annual service | Any make | £95 plus VAT |
Every figure on this site is an estimate based on published UK market ranges and our own installation experience. It is not a quotation. The price you are given after the free survey is the price you pay.
Other rooms
Bedrooms
A bedroom is the hardest room in the house to get right, and not because it is difficult to cool.
BedroomsLoft conversions
A loft conversion is reliably the hottest room in a London house, and it is hot for three reasons at once: the roof above it, the heat rising into it from the rest of the house, and insulation that was designed to keep warmth in during winter.
Loft conversionsConservatories
A conservatory is the one room where we will sometimes tell you not to buy air conditioning yet.
ConservatoriesSize any room
The calculator behind every figure on this page, in kW and BTU, with the working shown.
Sizing calculatorHome offices: common questions
Will people hear the air conditioning on a video call?
Not from a good unit running at its lowest speed. 19 to 24 dB(A) is below the background level of most rooms and well below what a laptop microphone picks up at arm's length.
What does get picked up is a unit cycling on and off, because the change is what a noise-suppression algorithm cannot mask. That is a sizing problem, and it is avoidable.
How much does it cost to run in a home office?
Roughly 12 to 22 pence an hour for a small office once the room is at temperature, so usually well under two pounds for a working day. The first twenty minutes cost more than the rest of the day, because that is when the unit is working hardest.
The running costs page has a calculator that uses your own tariff rather than an average.
Is a portable unit good enough for one room?
For occasional use in a rented flat where nothing can be fitted, it is better than nothing. For a room used every working day it is a poor trade: a portable unit has to vent through a window, the hose lets warm air back in, it is typically three to four times louder than a fitted split system, and it uses considerably more electricity for the same cooling.
The noise is usually what decides it for a home office. A portable unit in a room you take calls in is not workable.
Can I heat the office with it in winter?
Yes, and for a home office it is often the best reason to fit one. A home office is frequently a room the central heating serves badly, and heating one room with an air conditioner is far cheaper than heating the whole house to warm it, and cheaper than a plug-in electric heater in that room.
Free survey for a home office
We measure the room, do the heat load calculation properly, and give you a fixed written price with the model on it. If a smaller unit is the right answer, we will tell you.
Monday to Friday 9am to 7pm, Saturday 10am to 3pm, Sunday closed
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