Monobloc vs split vs portable, honestly compared
Published 17 Jul 2026
Split systems — the best cooling, the most permissions
An indoor unit and an outdoor condenser. Quietest indoors, most efficient, heats in winter (a unit that heats and cools is also what unlocks the permitted-development route for houses and — one per block — for flats). The cost is the outdoor box: freeholder consent for leaseholders, siting rules, and in some cases a planning application. If you can have one, have one.
Monobloc — the permission-shaped machine
Everything in one indoor unit, venting through two core-drilled holes. It exists for homes where the outdoor box is the blocker: leasehold flats, conservation frontages, freeholder refusals. Trade-offs, honestly: one room per unit; lower efficiency (all the machinery shares one small case); and the compressor is in the room with you — check the dB(A) figure before putting one in a bedroom. R290 versions contain no , so installation does not legally require an F-gas engineer.
Portable — the tonight machine
No permissions, works today, and systematically oversold: most UK units are single-hose, which pulls warm air back into the room as it runs — the full explanation here. Fine as a one-room, door-closed survival tool; wrong as a plan.
Which one is yours?
It depends on your building, your lease, and two planning rules most guides misquote. That is what the checker works out for your address.