Best air conditioning for your home: how to choose in the UK

Quick answer: For most UK homes the best choice is a fixed R32 split system, sized to the room's heat load, with a seasonal efficiency (SEER) of about 6 or higher, fitted by an F-gas certified installer who puts the warranty in writing. Portable units suit renters and one hot room. They are a poor whole-home answer.

Last checked 10 October 2026. The figures below come from the sources listed at the end, which we read on or shortly before that date.

How to choose home air conditioning, step by step

Most buyers start with a brand. Start with the room instead, because a well-sized unit from any approved installer network beats a badge on the wrong size of kit.

1. Pick the type

Many homeowners also want heating. A reversible split is an air-to-air heat pump that can do both, and Which? describes the two as the same technology. If heating matters, ask for the SCOP figure as well as SEER.

2. Size it in kW, not in headline BTU

Daikin UK's size guide gives a rule of thumb of about 0.1 kW per square metre for average ceilings and insulation. Its quick reference table:

Then adjust. Daikin says kitchens often need 10 to 20% more, a 3 m ceiling adds about 25% to room volume, and each person beyond two adds around 0.18 kW. It also notes a 30 m² room that needs 3 kW in Scotland could need 3.6 kW in the South East of England, a 20% rise. Brighton and Hove sits in that South East bracket. Daikin also lists insulation, window orientation and occupancy among the factors, so a sunny top-floor flat needs more than a shaded ground-floor one.

Getting the size wrong in either direction costs money: Daikin warns that skipping the space assessment risks a more expensive unit, higher running costs and reduced comfort. Use the size calculator for a first estimate, then ask the installer for a survey that accounts for your windows and ceiling.

3. Read SEER and SCOP properly

SEER is the seasonal efficiency of cooling and SCOP is the same for heating. Higher is better. UK law (retained Regulation 626/2011) sets the label classes for units up to 12 kW:

The label's yearly energy figure assumes 350 hours of cooling and 1,400 hours of heating in an average climate (Annex VII). A real example: the Daikin RXM35A/FTXM35A pair has a certified SEER of 9.25 and SCOP of 5.20 on the Eurovent register, with a 3.5 kW cooling capacity.

Brochures rarely turn this into pounds, so we will. At 26.32p per kWh (the Ofgem cap from 1 October 2026), that Daikin's 350 label hours of cooling use about 132 kWh, or roughly £35 a year. A unit at the bottom of A++ (SEER 6.1) would use about 201 kWh, roughly £53. The gap is about £18 a year for cooling. Heating is where efficiency pays more: on the same record, SCOP 5.20 against SCOP 4.00 is 673 kWh against 875 kWh over 1,400 label hours, about £53 a year. Both figures assume the certificate's design heating load of 2.5 kW (2.5 ÷ 4.00 × 1,400 = 875 kWh), so a larger load scales them up. If you only want summer cooling for a bedroom, do not pay a large premium for the top SEER. If the unit will also heat, do.

Work through your own numbers with the running cost estimator.

4. Check noise in the right unit

Datasheets quote two different things. Sound pressure is what you hear at a set distance, and sound power is what the unit emits. The UK energy label shows sound power in dB(A), per Annex III. The certified Daikin record above lists sound power levels of 58 dB(A) for both the indoor and outdoor unit in cooling. That number is not comparable with a sound pressure figure quoted at 1 m on a brochure, which will look much lower. Compare like with like, and ask for the indoor unit's sound pressure on its quietest setting if the unit goes in a bedroom. We did not find a UK government threshold for bedroom noise, so we do not quote one.

5. Choose R32, and know why

R32 is the refrigerant in most new residential splits. Its global warming potential is 675, against 2,088 for R410A (gov.uk and Daikin both give these figures). Since 2025, gov.uk says new single split systems containing under 3 kg of refrigerant must use gas with a GWP of 750 or less, which rules out R410A for most new single splits. R32 is classed A2L, meaning mildly flammable, and under UK health and safety law it is still treated as flammable (Cooling Post), so installers should be trained to handle it. That is one more reason to use an installer with proven F-gas credentials. See our F-gas register check guide.

6. Smart controls

Which? says air-to-air heat pumps are programmable and often come with a remote and a smart Wi-Fi option, and that many also offer dehumidification and air purification functions. A schedule is handy for cooling a bedroom before you go to bed and switching off at a set time. Check the app works with your phone, and that the unit still has a plain remote for when the Wi-Fi drops.

7. Warranty, and who fits it

This is where brand and installer meet, and it is the least understood part of buying. Manufacturers publish different terms, and for air conditioning several publish them only for installers. In most cases the long warranty depends on the installer's partner tier, on the unit being registered, and on regular servicing.

Manufacturer warranty terms in the UK, by brand

We read each manufacturer's UK pages on 10 October 2026. "Not published" means we opened the pages listed in our sources and found no UK warranty terms for residential air conditioning. That is an absence on the pages we read, not proof that no terms exist. Terms change, so ask the installer for the current wording in your quote.

Two things stand out. First, the longest numbers (7 and 10 years) belong to installers who have earned a partner tier, so "what tier is my installer?" is a better question than "which brand has the longest warranty?". Second, Daikin's residential warranty policy (July 2025) lists only its heat pump products and tells customers that for all other products the installer's own cover decides the terms. Get the warranty in writing, with the start date, parts and labour wording, and the servicing condition.

Our directory shows installer partner tiers only where the installer or the manufacturer's finder evidences them. See Daikin installers and Mitsubishi Electric installers.

What to avoid, rather than which brand to avoid

People often ask which AC brands to stay away from. We have no independent UK failure data on any brand, so we will not name one on rumour. These are the choices that go wrong in practice.

• Unbranded or marketplace-only units with no UK service agent. Manufacturers handle warranty claims through the trade. Toshiba's guidelines, for example, reserve their direct warranty process for installers with a credit account, and Daikin's policy sends residential buyers of air conditioning to the installer. A kit bought online and fitted by someone else may have no one to claim against.
• A new R410A single split. For most new single splits under 3 kg, GWP above 750 has been banned from sale in Great Britain since 2025 (gov.uk). If a seller still has one, ask why.
• A portable unit as the answer to a whole home. Which? describes portable units as bulky and heavy, and says most need a hose out of the window. Each one cools a single room, so a whole home needs several or a fixed system.
• Choosing on BTU alone. Capacity should match the room load (see step 2).
• An installer who cannot show F-gas certification. gov.uk says it is against the law to work with F gas without the right qualifications and company certification. Use the register steps in our F-gas register check guide.

A note for Brighton and Hove homes

Brighton is on the coast, and that affects the outdoor unit. Toshiba's warranty guidelines say high levels of nitrogen oxides and sulphur dioxide commonly occur within 3 miles of coastal locations and dense urban areas, and they recommend a protective coating on outdoor unit coils as a chargeable option. The same guidelines list coil corrosion from atmospheric pollutants as a warranty exclusion. Ask any installer, whatever the brand, whether coil protection is offered and whether the warranty excludes corrosion. Flats and conservation areas bring planning and lease questions of their own.

What to ask when you get quotes

1. Which exact model numbers (indoor and outdoor), with SEER, SCOP, and sound figures?
2. What partner tier do you hold with this manufacturer, and where can I check it?
3. What is the warranty period, who pays for labour, and what servicing does it require?
4. Can I see the F-gas company certificate and the fitter's personal certificate?
5. What size does your survey recommend, and why?
6. Is coil protection offered, given the coastal location?

Compare installers near you in the Brighton and Hove directory, or start with our Brighton and Hove installer directory.