Best air con for small offices in 2026

Small office cooling covers a wide range. A back-street solicitor with two rooms is a different job to a converted warehouse with 20 desks. Here is what the market recommends for 2026 broken down by office size.

Small office (under 50 square metres, 1-6 people)

Mitsubishi Electric MSZ or Mr Slim wall-mount

A commercial-spec wall-mount unit handles this size job cleanly. One outdoor condenser, one indoor head, cool and heat modes. The commercial-badged units (Mr Slim range) have heavier duty cycles than the domestic MSZ, which matters if the office runs from 8am to 7pm.

Fitted, £2,500 to £4,500 depending on install access.

Best fit for: home offices, small back-office rooms, one-room clinical spaces.

Medium small office (50-100 square metres, 5-15 people)

Daikin Sky Air single cassette

Ceiling cassette gives even air distribution across an open-plan space. One 5 kW indoor unit tucked into a suspended ceiling grid, one outdoor condenser on the rear wall or roof. Runs quietly, looks clean, distributes cool air evenly.

Fitted, £4,500 to £7,000.

Best fit for: converted terraces with suspended ceilings, small independent offices, single-floor units in mixed-use buildings.

Larger small office (100-200 square metres, 10-25 people)

Mitsubishi Electric Mr Slim twin cassette

Two cassettes share one outdoor unit. One goes at the front near the windows, one at the back to catch the wall-heat from copiers, servers and the kitchenette. Runs balanced regardless of external solar gain.

Fitted, £7,500 to £11,000.

Best fit for: full-floor offices in a converted terrace, first-floor commercial spaces, professional service firms.

Open-plan modern office (150-300 square metres)

Daikin VRV IV mini

VRV (variable refrigerant volume) lets one outdoor unit serve up to eight indoor cassettes with each zone controlled independently. The “mini” system is designed for exactly this size job - big enough to justify VRV, small enough to avoid the cost of full VRV IV.

Fitted, £15,000 to £22,000.

Best fit for: modern offices with mixed hot/cold zones (server room needs cooling year-round, main office needs heating in winter), tech companies, coworking spaces.

The five things that separate a good commercial quote from a bad one

1. Duty cycle sizing. Domestic-spec kit installed in a commercial setting fails in three years. Insist on commercial-badged units (Mitsubishi Mr Slim, Daikin Sky Air, LG Multi V S).
2. Redundancy plan. What happens if the compressor fails during a July heatwave? A good quote answers this. A cheap one does not.
3. Annual F-Gas service in the price. Commercial units above certain refrigerant thresholds are legally required to have annual leak checks. Get that quoted in year one.
4. Landlord permission. If you are in a rented commercial unit the outdoor condenser needs written landlord sign-off. Serious commercial installers ask about this on the first phone call.
5. Business insurance implication. Fitting air con changes the building’s insurance profile slightly. Notify your insurer, get a written confirmation of no premium change. Any decent installer will remind you.

What NOT to buy for a small office

• Domestic-spec kit installed by a domestic installer. Warranty voided the day it goes in, breakdowns in year two.
• The cheapest “commercial” quote. If a commercial quote is more than 20% below the average of three quotes, either the kit is undersized or the install skips corners.
• Portable industrial units as a stopgap. Fine for one week between installs. Expensive and disruptive as a solution.

Landlord permission - the paperwork you need

For a rented small office, get a short written letter from the landlord confirming:

• Permission to install one or more indoor units in the space you occupy.
• Permission to install the outdoor unit at a specified location (usually a rear wall or roof).
• Confirmation that the installation may remain at the end of the tenancy or, if the landlord requires removal, at whose cost.

Two paragraphs. Signed. Filed. That letter saves a month of dispute when you eventually move.

Get three commercial quotes

Tick “My business” at the top of the quote form and give us the floor area and rough headcount in the comments. We match small commercial jobs with installers who specialise in office and light retail work. Three fixed quotes back within 24 hours.