Which type of air conditioner is cheapest to run?

Mini-split (ductless) systems are the cheapest to run for a given cooling power because they have the highest efficiency, followed by split, then window units, with portables the most expensive per hour. For 12,000 BTU that's roughly £0.20/hr for a mini-split versus £0.35/hr for a portable in the UK.

What is the best type of air conditioner for a home?

For a room you cool every year, a mini-split is usually best — lowest running cost, quietest, and most also heat. For renting or moving cooling between rooms, a portable is the practical choice. A window unit is a cheap, self-installed middle ground if you have a suitable sash window.

Do I need an installer for a split air conditioner?

Yes. Split and mini-split systems have an outdoor compressor and refrigerant lines, so they normally need professional installation — but they are far more efficient over their lifetime. Portable and window units are DIY.

Which Type of Air Conditioner Should You Buy? Portable vs Window vs Split vs Mini-Split

Published: May 23, 2026 · Updated: May 25, 2026

There are four common air-conditioner types, and they all cool the same way — a compressor moves heat outside. Where they differ is install, efficiency and running cost. This is the overview that points you to the right one; for a specific head-to-head, jump to the focused comparison at the bottom.

At a glance

Type	Install	Efficiency	Running cost (12k BTU)	Best for
Portable	None — vent a hose, plug in	Lowest (EER ~8.5)	Highest (~£0.35/hr)	Renters, moving between rooms
Window	DIY into a window/wall opening	Medium (EER ~10.5)	Medium (~£0.28/hr)	One room, US-style sash windows
Split	Fixed, professional	High	Low (~£0.21–0.25/hr)	A room you cool every year
Mini-split	Fixed, professional	Highest (SEER 18–22)	Lowest (~£0.20/hr)	Long-term, whole-room comfort

UK figures at £0.245/kWh; US costs scale with the $0.16/kWh average.

The four types in brief

Portable — wheel it in, vent the hose, plug it in. Zero install and easy to store, but a single hose pulls cooled air out of the room, so it’s the least efficient type and costs the most per hour.
Window — sits in the opening and dumps heat straight outside, so it’s noticeably more efficient than a portable. Cheap and self-installed, but it blocks the window and needs a suitable (usually sash) opening.
Split — compressor outside, quiet head inside, linked by refrigerant lines. Needs a certified installer, but it’s efficient, quiet and usually heats too.
Mini-split — a ductless split with the highest efficiency and lowest running cost of all. The long-term pick for a room you cool every year.

Which should you buy?

Renting, or need to move cooling between rooms? → Portable.
One room, and you have a usable sash window? → Window.
Cooling the same room for years and can install? → Mini-split — the lowest cost to run, and it heats in winter.
Whole house, building or renovating? → A ducted or multi-zone split.

Compare any two, head-to-head

Narrowed it to two types? Each guide below is the focused decision — running cost, install and the break-even for that specific pairing:

Portable vs window — the two no-installer options
Portable vs split — flexibility vs lower running cost
Portable vs mini-split — the biggest efficiency gap
Window vs split — DIY vs quieter and more efficient
Mini-split vs window — cheap-and-easy vs efficient-and-permanent
Split vs mini-split — ducted vs ductless, decoded

Then compare the actual units by what they cost to run: portable, window, split and mini-split — all ranked by cost per hour. See also the running-cost guide and BTU sizing guide.