Portable air conditioners with no outdoor unit (UK, 2026)

Updated: July 2026

Most UK homes have no fixed air conditioning, so when a heatwave hits, the units that actually work in a flat or rented house are the ones that need no outdoor unit. This guide explains what those units are, how portable, window and all-in-one models differ, why they vanish from the shelves so fast, and how to get one before it sells out again.

What “no outdoor unit” actually means

A traditional “split” air conditioner has two parts: an indoor unit and a separate outdoor condenser, joined by pipework drilled through the wall. That is fine for a house you own, but it needs professional installation and — for most renters and flat dwellers — the landlord’s permission and a fixed external wall.

A no-outdoor-unit air conditioner puts everything in one indoor box. You’ll also see these called monoblock units, because the whole refrigeration system is a single block rather than a split pair. There is nothing to mount outside, nothing permanent to install, and in most cases nothing that needs an engineer. That convenience is exactly why they are the default choice for cooling a British home.

Portable vs window vs all-in-one

“No outdoor unit” covers three practical formats. They all avoid an external condenser, but they mount and vent differently:

Portable air conditioners are free-standing units on castors. A flexible exhaust hose hooks over an open window to push warm air outside. Nothing is fixed in place, so you can wheel the unit from room to room — the most popular option in the UK.
Window air conditioners sit in a sash or casement window opening and vent heat straight outside through the back of the unit. They cool efficiently for their size but need a suitable window and a bracket, so they are less common here than portables.
All-in-one air conditioners (monoblock or through-wall) are a single indoor box vented through a small pair of holes in an external wall. Once fitted they are tidy and quiet, with no hose draped across the room.

If you rent, or you just want something you can set up today, a portable unit is usually the easiest. If you own and want a permanent, tidier result, an all-in-one is worth the extra fitting. Read the dedicated pages above for the trade-offs on each.

Why they sell out in heatwaves

Because so few UK homes have built-in cooling, demand is dormant for most of the year and then spikes overnight the moment a heatwave is forecast. Retailers stock for a normal British summer, not a record-breaking one, so popular models can go from “in stock” to “sold out” within hours — sometimes minutes for the best-value units. Restocks arrive in unpredictable batches and disappear just as fast, which is why refreshing a shop’s page by hand rarely works.

How to get one before it’s gone

The reliable way to buy during a heatwave is to be told the instant a unit is back, rather than checking manually. That is what BunnyDing does: you pick the air-conditioner types and shops you care about, pay once (no subscription), and we watch the retailers around the clock. The moment a matching unit is buyable again, you get an email with a direct link so you can check out before it sells out.

Get restock alerts

Which UK shops stock them

We currently watch 13 UK retailers for air-conditioner stock. Each has its own restock-alert page describing what we cover:

Note: BunnyDing is an independent alert service and is not affiliated with any retailer. We describe what we watch and link you out to buy — we never sell air conditioners ourselves. See the all-in-one, portable, window type pages for detail on each.