Home air conditioning was once considered a luxury confined to commercial buildings and new-build flats in the UK. That has changed rapidly. Warmer summers, more people working from home, and the falling cost of inverter-driven split systems mean that domestic AC installation has grown substantially since 2020, and continues to grow in 2026.
The key question is what type of system suits your home, and what it will cost. A portable fan is not air conditioning; a fixed split system is. Understanding the difference, and the options in between, helps you spend your budget wisely.
Air Conditioning Cost Summary
| System type | Supply & install cost (inc. VAT) | Best for |
|---|---|---|
| Portable evaporative cooler | £100–£400 (no install) | Very limited cooling, rental |
| Portable refrigerant AC (window/floor) | £300–£800 (minimal install) | Single room, temporary |
| Single-split AC system | £1,200–£2,500 | One room, year-round use |
| Dual-split (2 indoor units, 1 outdoor) | £2,500–£4,000 | Two rooms |
| Multi-split (3–5 indoor, 1 outdoor) | £4,000–£9,000 | Whole-house |
| Ducted (concealed) system | £6,000–£15,000+ | New-build or major renovation |
| Air-to-air heat pump (combined heating/cooling) | £1,500–£3,000 per room | Year-round heating and cooling |
Types of System Explained
Portable Air Conditioners
Portable refrigerant ACs are self-contained units that sit in the room, extract heat from the air, and exhaust it via a flexible hose vented through a window or small hole in the wall. They require no permanent installation (though a through-wall vent is neater than dangling a hose out of a window) and cost £300–£800 to buy.
Their key limitation is efficiency: because they draw in warm room air to cool the condenser, they partially counteract their own cooling effect. They are significantly less efficient than split systems (lower SEER/SCOP ratings) and considerably noisier. They are best treated as a stopgap rather than a permanent solution.
Split Systems (Most Popular)
A split system consists of two units: an indoor air handler (wall-mounted, floor-standing, or ceiling cassette) and an outdoor compressor/condenser connected by refrigerant pipework run through a small hole in the external wall. They are quiet, efficient, and, on modern inverter-driven models, can also provide efficient heating in winter (functioning as an air-to-air heat pump).
Modern split systems have SEER (Seasonal Energy Efficiency Ratio) values of 7–9 for mid-range units and up to 12 for premium inverter systems. By comparison, a portable AC typically achieves SEER 2–3.
Installation requires a qualified and F-gas registered engineer; the refrigerant circuits must be installed, pressure-tested, and commissioned by a certified operative under the F-Gas Regulation (EU 517/2014, retained in UK law post-Brexit as the UK F-Gas Regulation).
Single-room split system installed costs in 2026:
| Room size | Capacity required | Installed cost (inc. VAT) |
|---|---|---|
| Small bedroom (up to 15 m²) | 2.0–2.5 kW | £1,200–£1,800 |
| Double bedroom / small lounge (15–25 m²) | 2.5–3.5 kW | £1,500–£2,200 |
| Large lounge / open-plan (25–45 m²) | 4.0–6.0 kW | £2,000–£3,000 |
| Very large open-plan (45–80 m²) | 6.0–9.0 kW | £2,800–£4,500 |
Capacity should be calculated by a qualified installer using a heat gain calculation, online rules of thumb can be misleading, particularly in south-facing rooms or properties with poor insulation.
Multi-Split Systems
A multi-split system uses a single outdoor unit connected to two to five indoor units in different rooms. The outdoor unit is larger (and more expensive) than a single-split outdoor unit, but the economy of sharing one compressor and one refrigerant circuit becomes apparent when covering three or more rooms.
Installed cost in 2026:
- 2 rooms, £2,800–£4,500
- 3 rooms, £4,000–£6,500
- 4–5 rooms, £5,500–£9,000
The brands most commonly installed by UK engineers include Daikin, Mitsubishi Electric, LG, Panasonic, and Samsung. These are not equivalent to budget-end brands sold via retail; quality and reliability differ significantly.
Ducted Systems
Concealed ducted air conditioning distributes conditioned air through a network of ducts in the ceiling or floor void. The indoor unit is hidden in a loft or ceiling space; only the grilles are visible. This is the most discreet option and suits whole-house conditioning, but it requires either a new-build shell or significant structural work to install ducts retrospectively.
Costs are high: £8,000–£15,000 for a three- to four-bedroom house, with additional costs for any structural work to accommodate the ducting.
Planning Permission
Permitted development rights in England allow the installation of air conditioning equipment on a house without planning permission, subject to conditions:
- No equipment on a wall or roof facing a highway
- The equipment must not project beyond a wall or roof
- The volume of all installed equipment must not exceed 0.6 m³ per wall
- Properties in Article 2(3) land (conservation areas, AONBs, World Heritage Sites) require specific authorisation
Most domestic single-split and multi-split installations fall within permitted development. Always check with your local planning authority if the property is listed or in a conservation area.1
Running Costs
A 3.5 kW split system running for 8 hours per day during a 3-month summer season costs approximately:
- At 30p/kWh (approximate UK average in 2026): £30–£45 per month on air conditioning mode
- In heat pump (heating) mode in winter, running costs are typically 2–3× cheaper than an equivalent electric resistive heater for the same heat output, owing to COP values of 3–4
Annual running cost for a well-specified single-room system used as both cooling and supplemental heating is roughly £200–£400 per year depending on usage pattern and electricity tariff.
Choosing an Installer
- The installer must hold an F-gas qualification (City & Guilds, BESA, or REFCOM certification) to handle refrigerants legally, ask to see the certificate before accepting a quote
- Look for membership of the BESA (Building Engineering Services Association) or ACRIB (Air Conditioning and Refrigeration Industry Board)
- Obtain at least two quotes; a written specification including the make, model, kW capacity, and estimated SEER rating of the proposed system
- Confirm whether the quote includes an electrical spur (if one is not already available adjacent to the outdoor unit location), this is sometimes excluded
- Ensure a warranty on both labour and parts (manufacturers typically offer 3–7 years on registered installations)
References (1)
Figures in this note were checked against the sources below on 14 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.
- 1technicalvery strongThe National Archives, legislation.RN-OWGIY3Schedule 2 Part 1 of the GPDO 2015, development within the curtilage of a dwellinghouse. This is permitted development itself: Class A enlargement and alteration, with the limits and conditions, through the classes covering roof alterations, porches, outbuildings and hard surfaces. Every statement about what can be built without planning permission traces to this Part, and the exclusions at the start of each class are where most projects actually fall out.
-
The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, The National Archives, accessed 14 September 2026. legislation.gov.uk
