A single-hose portable feels cheaper because the shop price is in the high hundreds at most, often less, while a surveyed split is an installed system in the high hundreds to low thousands. On electricity, the portable usually loses. It sits in the room, dumps heat through a hose, and pulls new warm air in through the gaps. Many portables draw around 1 kW electrical or more for a modest cooling effect. A split puts the compressor outside and can deliver more cooling for a lower electrical draw. Multiply either by your tariff. Buy a portable for odd days. Buy a split, via an F-gas installer, for a room you cool all summer.
A hose in the room, a compressor outside
A portable with one exhaust hose blows some of the room's air outside after it has cooled the coil. Replacement air leaks in from the rest of the house, often warm. The compressor is in the room, so its noise and some of its heat are with you. The plug load is commonly in the 0.9 to 1.5 kW class on models people actually buy. Four hours is roughly 4 to 6 kWh for cooling that may still lose in a sunny room. A small split's electrical draw while holding a bedroom is often lower than that, for a larger cooling capacity, because the heat is rejected outdoors and the machine is built as a proper air-to-air heat pump. Energy Saving Trust describes that arrangement. The exact figure depends on weather and setpoint. The pattern is stable: the split gives more comfort per unit of electricity. Shop price and running cost point in different directions. Your pence per kWh scales both bills. It does not close the efficiency gap.
An illustration you can scale from your bill
The input watts on the label are the start of the sum, not the whole running cost.
- Single-hose portables fight air they have just sucked in.
- Splits reject heat outside.
- Take 1.2 kW for a portable and 0.7 kW electrical for a split as a teaching illustration, not a lab result.
- Over five hot nights of eight hours, that illustration is 48 kWh against 28 kWh.
Fourteen pounds against eight, and a warmer room
At 30 pence per kWh that five-night illustration is about fourteen pounds versus about eight pounds, and the portable may still be the warmer room. At a cheaper night rate the gap in pounds shrinks and the comfort gap remains. None of these illustrations are a tariff. Read your bill.
Two hoses still sit in the room
A dual-hose portable wastes less air than a single hose and is still noisier and usually less efficient than a fixed split. Two-hose models waste less conditioned air. They still sit in the room and usually trail a proper split on noise and efficiency. The label does not say whether the room will actually become comfortable.
Odd nights, a let, and a house you are leaving
A rented room where consent for an outdoor unit will never come, a house you will leave this year, or a spare room used on four nights a year can justify a portable you vent safely. The hose must actually go outside. A hose in a bucket or a cracked window with the gap unsealed is how the room stays hot. A portable that never opens a refrigerant circuit avoids F-gas duty and also avoids outdoor planning. It does not become the efficient option.
Stop buying a portable for every night of the summer
The portable is usually not cheaper to run. It often draws more electricity for less cooling. It is cheaper to buy. Over a full summer of nights the electricity gap is real, and the split is quieter. The moment you want quiet sleep all summer, the split's install cost is the purchase that cuts running cost and noise. That install is GOV.UK F-gas work. Choose the installer for survey quality, not for a logo that claims tiny running costs. The Planning Portal heat pump notes apply to the outdoor unit you would then be siting.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.