Independent comparisons. We may earn from shop links. More info

Split air conditioner buying guide

Updated: October 2026

A useful split air conditioner buying guide helps you reject misleading numbers before they shape the shortlist. The nine amazon.co.uk listings in our [split air conditioner comparison](/hub/cooling/split-air-conditioner) mix wall systems, portable splits, cooling-only machines and heat pumps, and their specification fields are not consistently comparable. Start with the room and the installation you can complete, then check capacity, energy-label figures and the conditions on any noise claim. This page explains those trade-offs. It does not name a winner or replace an installer’s heat-load calculation. Listings were checked on 15 October 2026. We did not run a lab test. A purchase through our links may earn a commission at no extra cost to you.

A useful split air conditioner buying guide helps you reject misleading numbers before they shape the shortlist.

Our top picks

Midea Midea PortaSplit 12,000 BTU

Best overall

Midea Midea PortaSplit 12,000 BTU
9.2/10about £1,099.99
View offer
Generic Generic 12,000 BTU wall split AC12000

Preis-Tipp

Generic Generic 12,000 BTU wall split AC12000
7.8/10about £500
View offer
Generic Generic 24,000 BTU wall split WC18

Alternative

Generic Generic 24,000 BTU wall split WC18
6.5/10about £849.99
View offer
On this page
  1. 1.What you are actually buying
  2. 2.Size the room, not the title
  3. 3.Cooling only or a heat pump
  4. 4.Numbers worth keeping

What you are actually buying

A split moves heat between two sections. The cold coil stays in the room, and the condenser rejects heat outdoors. A wall split joins them with refrigerant pipes. A portable split uses a factory-connected hose to a temporary outdoor position. Both differ from a single-hose portable, which sends room air out through a window hose and draws replacement air back in. The same BTU headline does not make two products equivalent. The Midea PortaSplit and several wall units state 12,000 BTU or about 3.5 kW. The Midea uses an approximately 2 m fixed connection, and normal setup needs no drilled refrigerant joint. A wall split needs an outdoor position and qualified refrigerant work. If you are still choosing between a split and a hose unit, read split air conditioner vs portable air conditioner first.

Size the room, not the title

Capacity should match the heat load, not the largest BTU you can afford. As a rule of thumb, allow roughly 100–150 W of cooling per square metre. That is only a starting point. Sun, glazing, insulation, ceiling height, cooking and several occupants can all raise the requirement. The same floor area can still be two different jobs. Where the fields agree, 12,000 BTU is about 3.5 kW, and the 24,000 BTU machines claim about 6.8–7.0 kW. Seller areas run from 20 m² to 42 m² and are not a universal chart. One 9,000 BTU model says up to 22 m². A 12,000 BTU model says 25 m². Oversizing adds cost. Undersizing can leave the compressor running without reaching the target. Ask the installer to confirm the load, then use the best split air conditioner page.
Midea Midea PortaSplit 12,000 BTU

Testsieger

Midea Midea PortaSplit 12,000 BTU
9.2/10about £1,099.99
View offer

Cooling only or a heat pump

Most wall splits here claim heat-pump heating as well as cooling. The Midea PortaSplit also heats. The two 5,000 BTU portable splits describe cooling only. If you only need summer cooling, the simpler product may be enough. If you want shoulder-season heat, check the operating range and the heating label. The Midea UK page states a heating range of −10°C to 30°C. One generic 12,000 BTU listing prints −15°C to 50°C. That is a seller statement, not a cold-weather test. For heating, look for SCOP for the Average climate season. For cooling, look for SEER and the cooling class. Heating can also change planning, which the split air conditioner installation guide covers.

Numbers worth keeping

Under the applicable label scale, A++ cooling begins at SEER 6.10 and stays below 8.50. SEER 6.1 or 6.2 beside A++ is a credible pair. The WC18 listing’s SEER 16.0 beside A++ is not usable. Ask for the physical label. The word inverter describes compressor control. It is not proof of a stated percentage saving. Noise cells show 22, 27, 39 and 54 dB, plus an impossible 1 dB entry. They do not consistently name the section, sound power or pressure, distance or mode. Midea’s 39 dB(A) is silent mode at 1 metre, and one reviewer says full cooling is louder. The 60 dB(A) indoor and 65 dB(A) outdoor limits up to 6 kW are sound-power caps, not an Amazon cell. Note the output, the heating need, labelled SEER and SCOP, separate noise figures, and the installation route before you compare prices.

Common questions

How do I size a split air conditioner for one room?
Measure the floor area and use roughly 100–150 W per square metre only as a first estimate. Then account for glazing, sun, insulation, ceiling height, occupants and heat-producing equipment. An installer’s heat-load calculation should settle the final capacity, particularly for an exposed room or an open-plan space. Two rooms with the same floor area can still be different jobs.
Is the biggest BTU figure the right choice?
No. BTU describes nominal output, not suitability, quietness or installation quality. In this set, 12,000 BTU pairs with about 3.5 kW where the fields agree, and 24,000 BTU with about 6.8–7.0 kW. Match the output to the calculated room load, and confirm the outdoor unit can be sited. A larger title does not repair a thin listing.
Can I trust a seller’s square-metre figure?
Treat it as a screening clue, not a guarantee. Seller areas here run from 20 m² to 42 m² and usually omit sun, insulation, ceiling height and occupancy. One 9,000 BTU model says up to 22 m² and a 12,000 BTU model says 25 m². Compare that claim with a heat-load estimate and the manufacturer’s technical data before you treat it as the room limit.
What SEER should appear with A++ cooling?
On the relevant label scale, A++ cooling corresponds to SEER from 6.10 to below 8.50. Values of 6.1 or 6.2 beside A++ are coherent. A marketplace field showing SEER 16.0 beside A++, as on the WC18 listing, should be checked against the physical energy label before it influences your choice. Do not calculate a saving from that cell.
Does inverter technology guarantee lower bills?
No. An inverter lets the compressor vary its output instead of only switching fully on and off. The word alone does not quantify consumption, and it is not proof of a stated percentage saving. Use the seasonal efficiency and the energy label, then consider how often and at what temperature you will run the system.
Why do the Amazon noise figures conflict?
They may describe different measurements, or they may omit the conditions. Cells in this set include 22, 27, 39 and 54 dB, plus a 1 dB field that cannot be used. Ask for figures that name the indoor or outdoor section, the mode, the measurement type and the distance. Sound-power limits in the regulation are a different number from an unexplained Amazon cell.

Related pages

Split air conditioner for a bedroom

Split air conditioner

Best split air conditioner: wall, portable or skip

Split air conditioner installation rules in the UK

Split air conditioner vs portable: three UK machines

Sources

Public UK sources and the manufacturer page below. amazon.co.uk listings checked on 15 October 2026.

  1. GOV.UK: qualifications required to work on equipment containing F gas (retrieved 15 October 2026)
  2. GOV.UK: selling F gas or equipment (retrieved 15 October 2026)
  3. Planning Portal: planning permission to add air conditioning (retrieved 15 October 2026)
  4. legislation.gov.uk: England GPDO Class G (retrieved 15 October 2026)
  5. GOV.UK: building work, replacements and repairs to your home (retrieved 15 October 2026)
  6. legislation.gov.uk: Regulation (EU) No 206/2012 (retrieved 15 October 2026)
  7. legislation.gov.uk: Regulation (EU) No 626/2011 Annex III (retrieved 15 October 2026)
  8. GOV.UK: noise nuisances and how councils deal with complaints (retrieved 15 October 2026)
  9. Midea UK: PortaSplit air conditioner (retrieved 15 October 2026)