Short answer: Portable air conditioners are cheap and need no installation, but they are noisy, less efficient and vent hot air through a hose in a window. A fixed split system costs more to buy and fit, but it cools far better, runs quietly, heats efficiently in winter and is cheaper to run.
How they differ
A portable unit has the compressor in the room with you and dumps heat through a hose, while pulling in warm air through gaps to replace what it expels. A split system puts the compressor outside and moves heat through sealed pipes, so it is quieter and much more effective.
When a portable makes sense
For a renter who cannot fix anything to the walls, a short-term need, or a room that only overheats a few days a year. Single-hose portables are the least efficient; dual-hose models are better.
When a fixed system makes sense
If a room overheats every summer, if you need quiet for sleep or work, or if you want efficient winter heating as well. Over a few summers the lower running costs and the heating benefit narrow the gap in price.
Related services
More guides
- How much does air conditioning cost to install in the UK?
- How much does air conditioning cost to run?
- What size air conditioner do I need?
- Do you need planning permission for air conditioning?
- The £2,500 grant for air-to-air heat pumps explained
- F-gas rules: what homeowners need to know
- R32, R410A and R22: refrigerants explained
- Is air conditioning the same as a heat pump?
- What happens on air conditioning installation day
- Air conditioning noise and your neighbours
- Looking after your air conditioning: an owner's checklist
- Can you fit air conditioning in a listed building?
- Air conditioning in a flat: leases, freeholders and planning
- Keeping a home cool in a heatwave
- Multi-split or separate single systems?
Reviewed October 2026. Rules and prices change; check the date and ask us if anything is unclear.