Every figure checked against its source on 7 November 2026
Portable or fixed air conditioning: which is right for you?
A portable costs a fifth of a fitted unit and needs nobody's permission, which makes it the right answer for a tenant, a student or anyone who needs one room survivable this week. A fixed split cools far better, more quietly and for less electricity. This guide sets the two side by side for a Dartford home.
Get a price
Three details and we call you back with the next step.
What does each cost?
Checkatrade puts a 12,000 BTU portable at £300 to £420, and a 12,000 BTU wall unit at £750 plus £1,150 to fit, which we make about £1,900, with £400 to £700 of electrics on top. The portable needs only a socket, a window and a hose. Source: Checkatrade.
Why does a portable cool so much less than its label says?
Because of the hose. A single-hose portable blows its hot air out through a window, and every litre it pushes out is replaced by a litre of warm air sucked into the room from outside or from the rest of the house. The hose itself is warm and radiates heat back into the room. The compressor is indoors too, adding its own heat and its own noise. The label capacity is the machine's; the room sees a good deal less.
How do noise and running cost compare?
A portable has its compressor beside your bed, where a split has only a fan and a coil, so a split is much quieter at night. On efficiency, the Energy Saving Trust gives a typical seasonal cooling efficiency of around 7 for air-to-air systems; a portable, working against its own hose, delivers a fraction of its power as useful cooling, so the same comfort costs more electricity at the same 26.32p per kWh. Sources: Energy Saving Trust; Ofgem.
When is a portable the right buy?
- You rent and the landlord says no to anything on the wall.
- You own a flat whose freeholder has refused consent and a monobloc is not worth it.
- You need one room usable this week, during a heatwave, before anyone can survey.
- You will move within a year or two.
Private renting covered 18.1% of Dartford households at the 2021 Census, so a portable is the honest recommendation for a good share of the people who ring us. Source: ONS.
When does a fixed unit pay?
When you own the wall and plan to stay. It cools properly, it is quiet enough for a bedroom, it heats the room in winter for about a quarter of what the portable's cousin, the fan heater, costs, and it does not block a window. Over several summers the running cost difference closes much of the price gap. Read the cost guide, then our air conditioning in Dartford page for how a job runs. Source: Energy Saving Trust.
Questions people ask
Do two-hose portables fix the problem?
Partly. They draw air for the condenser from outside instead of from the room, which stops the suction effect, but the compressor and the hoses are still indoors.
Can you install a window kit so the portable seals better?
A sealed window panel helps and costs little. It is still a portable; it does not become a split.
Will you buy my portable off me when I go fixed?
No, but keep it: a portable in the spare room during a heatwave is a sensible use for it.
Sources we checked
Worth knowing before you ring
With these we can usually tell you on the first call whether the job is simple.
- The postcode
- Whether it is a house, a flat or business premises, and roughly its age
- If you rent or lease, who owns the external wall
- Which room, how big, and the direction its window faces
- Any management company, conservation area or listing that applies
Decided? Our air conditioning in Dartford page covers what we install, what we maintain and where we go.
The services this guide leads to
Home air conditioning
The back bedroom, the new flat with the glass wall, the loft nobody can sleep in: cooled in summer, warmed in winter.
Air conditioning installation
The whole job from the first measurement to the handover of the remote, with every consent checked on the way.
Air-to-air heat pumps
The same wall unit, run the other way: a room heated for pence an hour, with the summer cooling thrown in.
Other guides
What does air conditioning cost to fit and to run?
Where the money goes: the unit, the labour, the wiring, the electricity, and the extras a flat or a new estate brings.
Air conditioning and planning permission: the rules for England
Every permitted development condition in one table, then the twists Dartford's new estates and conservation areas add.
Air conditioning with no outdoor unit: how monoblocs work
The through-the-wall units for flats and blocks that cannot take an outdoor box.
Air conditioning in a flat: who has to agree, and in what order
Lease, freeholder, management company and planning, in the order to tackle them.
Bedroom air conditioning: what it does for sleep, and what it costs
The sleep threshold, noise at night, sizing and the price of a quiet bedroom.
Cooling a loft conversion: the options that work
Why lofts cook, the free fixes first, then where a unit goes on a dormer.
What size of air conditioner does a room need?
Kilowatts and BTU by room size, with the adjustments that matter.
How to check an air conditioning installer on the F-gas register
The company certificate, the engineer's category and where to look them up.
Want us to ring you?
A name, a number and a postcode is enough. Say which room if you can. Or ring 01322 952910.