Home offices are often the box room, a converted loft or a corner of the house no one else wanted. They’re small, they often face the sun, and they’re full of equipment that turns electricity into heat. Unlike a living room, you can’t just go and sit somewhere cooler when the afternoon gets hot.
This guide covers why home offices overheat, how a unit is sized, where it should go so it doesn’t blow on you or hum through your calls, how it can heat the room in winter, and what installation involves.
Why home offices get so hot
- Sun. A south or west facing window can let in a lot of heat in the afternoon.
- Equipment. Computers, monitors, docks and printers turn almost all the power they draw into heat.
- You. A person sitting at a desk all day adds heat too.
- The room. Small rooms, loft rooms and rooms with little cross-ventilation heat up fastest.
Cheap fixes help first: blinds or external shading, turning off equipment you aren’t using, ventilating in the cool of the morning. If the room is still too hot, cooling is the answer.
Sizing the unit
Wall-mounted units come in steps of capacity, for example 2.5 kW, 3.5 kW and 5 kW. Home offices are often small enough for the smallest sizes in a range, but the right size comes from a heat load check, not floor area alone. We look at the room size and ceiling height, the glazing and which way it faces, insulation, roof exposure in loft rooms and how much equipment you run.
Bigger isn’t better. An oversized unit cools in short bursts, which feels less comfortable and handles humidity less well. Our guide on choosing the right size unit explains more.
Where the unit should go
Position matters more in a home office than almost anywhere else, because you’re sitting in the same spot for hours. We avoid placing the unit directly above or in front of the desk. A wall opposite or to the side, with the louvres set to spread air across the ceiling, works well. We also think about the outdoor unit: keep it away from the office window, so you don’t hear it on calls, and away from neighbours.
For video calls, use a low fan speed or quiet mode. Our noise guide explains the figures.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
Heating in winter, too
Most split systems are reversible. The Energy Saving Trust notes that air-to-air heat pumps are sometimes referred to as air conditioning. In heating mode the same unit can warm the office efficiently, so you may not need to heat the whole house just to work in one room. See using heat pump mode in winter.
Fresh air still matters
A split system recirculates and cools the air in the room. It doesn’t bring in fresh air. In a small office with the door shut, open a window or trickle vent between calls, or consider ventilation.
Installation basics
- A pipe route from the indoor unit to the outdoor unit, usually through one core hole in an outside wall.
- A condensate drain that falls to a suitable outlet, or a small pump where it can’t; see condensate pumps.
- An electrical supply. A new circuit must meet Building Regulations Part P; our work is done under our NICEIC approval. See new circuits and Part P.
- Planning: an outdoor unit used for heating as well as cooling may be permitted development on a house if it meets the Planning Portal’s conditions; cooling-only units aren’t covered.
For an office in the garden, see our garden rooms guide.
What it costs
A single room split system costs £1,200–£2,200 + VAT, including supply, installation, commissioning and F-Gas documentation. HMRC’s Notice 708/6 zero-rates air source heat pumps installed in homes until 31 March 2027, and says most air conditioning units are air source heat pumps, but each case depends on its facts. We confirm the VAT on your quote.
Quick answers
What size air conditioning unit does a home office need?
Often one of the smaller wall units, but it depends on the room, the glazing, the sun and your equipment. We check the heat load at the survey.
Will the air conditioning be audible on video calls?
On a low fan speed a good indoor unit is quiet. We also keep the outdoor unit away from the office window.
Can I use the unit to heat my office in winter?
Most split systems are reversible heat pumps, so yes, and it means you may not need to heat the whole house to work in one room.
How much does home office air conditioning cost?
A single room split system costs £1,200–£2,200 + VAT, fully installed and commissioned. We confirm the VAT on your quote.
Related services
- Air conditioning installation
- Wall-mounted air conditioning
- Air-to-air heat pumps
- Domestic air conditioning
More advice
- Air Conditioning for Garden Rooms and Outbuildings
- How to Choose the Right Size Air Conditioning Unit
- Air Conditioning for Loft Conversions
- Air Conditioning Noise: How Quiet Are Modern Systems?
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.