When a heatwave hits, portable air conditioners sell out fast. They have a place, and we’re not going to pretend otherwise. But they’re a different kind of machine from a fixed split system, and it helps to understand why before you decide which suits you.
How a portable unit works
A portable air conditioner puts the whole refrigeration system in one box on wheels: compressor, both coils and fans. It cools the room air passing over one coil, and blows the heat it has collected out of a hose that goes through a window or a wall vent.
Most portables have a single hose. To carry the heat out, they take air from the room and push it outside. That air has to be replaced, so warm air is drawn in from outside or from the rest of the house through gaps around doors and windows. Some of the cooling is lost straight away. The hose itself gets warm and gives some heat back to the room. Dual-hose models reduce the problem by drawing outside air for the hot side, but they’re less common.
How a fixed split system works
A split system separates the noisy, hot parts from the room. The indoor unit holds a coil and a quiet fan; the compressor and the heat-rejecting coil sit outside. The two are linked by sealed refrigerant pipes through a small hole in the wall. Nothing in the room is fighting against itself, no window needs to stay open, and the room isn’t pulling in warm air from elsewhere. Our plain English guide explains the cycle.
Side by side
| Portable | Fixed split | |
|---|---|---|
| Upfront cost | Low, buy from a retailer | Higher: supplied, installed and commissioned |
| Installation | Plug in, fit the window kit | Survey, installation by an F-Gas certified company |
| Noise in the room | Compressor is in the room | Compressor is outside; indoor fan only |
| Cooling on hot days | Reduced by warm air drawn back in | Rated capacity delivered to the room |
| Heating | Some models | Most modern units are heat pumps |
| Security | Window must stay partly open for the hose | Windows can be shut and locked |
| Water | May need a tank emptying | Condensate piped away |
| Floor space | Takes floor space | High on the wall or in the ceiling |
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.
Running costs
Comparing running costs honestly means comparing the same amount of cooling. Manufacturers publish efficiency figures for both types, but under different test methods, so headline numbers aren’t directly comparable. What we can say is that a fixed split avoids the warm air drawn in by a single-hose portable, has an inverter that slows down once the room is cool, and keeps the compressor’s heat outside. In practice that usually means less electricity for the same comfort.
To work out the cost of any unit yourself, take its power draw in kW, multiply by the hours it runs, and multiply by your electricity unit rate. A unit drawing 1 kW for 5 hours uses 5 kWh; multiply that by the pence per kWh on your bill.
Refrigerants and the rules
Under GOV.UK’s rules on F gas bans in new equipment, movable (portable) air conditioning containing HFCs with a global warming potential above 150 can’t be placed on the market, so portables now on sale use low-GWP refrigerants. Fixed systems mostly use R32. A portable is sealed at the factory and needs no F-Gas engineer to set up; a fixed system must be installed by an F-Gas certified company.
There’s a VAT difference too. HMRC’s Notice 708/6 says air source heat pumps can qualify for the zero rate on energy-saving materials in homes if they’re permanently fixed, not portable. We confirm the VAT on a domestic split system on your quote.
When a portable makes sense
- You rent and can’t make alterations, and your landlord won’t agree to a fixed system.
- You need cooling for a few days a year in one room.
- A short-term need, such as a hot spell during a building project or an event. For businesses, air conditioning hire may suit better.
- A stopgap while a fixed system is being planned.
When a fixed system is the better choice
If you want a quiet bedroom, a home office you can work in all summer, heating as well as cooling, or a room you can lock up at night, a split system does the job properly. A single-room split is £1,200 to £2,200 + VAT with us, including supply, installation, commissioning and F-Gas documentation. Our guide to hire versus installation covers the in-between options.
Quick answers
Are portable air conditioners as good as fixed ones?
For occasional use in one room, a portable can take the edge off. For regular use, a fixed split is quieter, keeps windows shut and usually cools better for the same electricity.
Why is my portable air conditioner so loud?
The compressor is inside the unit, in the room with you. A split system puts the compressor outside.
Do portable air conditioners need a window?
Most need the hose to go outside, through a window kit or a wall vent. That means the window can’t be fully closed and locked.
Related services
- Air conditioning installation
- Wall-mounted air conditioning
- Air conditioning hire
- Domestic air conditioning
More advice
- Air Conditioning Hire vs Permanent Installation
- Air Conditioning for Bedrooms: Complete Guide 2026
- How Much Does It Cost to Run Air Conditioning in the UK? 2026 Guide
- DIY Pre-Charged Air Conditioning Kits: What the F Gas Rules Say
- 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.