Every figure checked against its source on 7 November 2026
What does air conditioning cost to fit and to run?
Add up Checkatrade's national figures of May 2026 and one wall unit with its electrics comes to roughly £2,300 to £2,600; that sum is ours, not Checkatrade's. Neither is it our price, and a Dartford flat needing a licence to alter, or a new-build whose only permitted outdoor position is a long way from the room, can come to more. This guide follows the money.
Get a price
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How much are the unit and the labour?
| Capacity | Unit | Labour | Our total |
|---|---|---|---|
| 12,000 BTU (about 3.5kW) | £750 | £1,150 | About £1,900 |
| 18,000 BTU | £940 | £1,150 | About £2,090 |
| 24,000 BTU | £1,090 | £1,150 | About £2,240 |
The unit and labour columns are Checkatrade's, for one split on a brick wall; the right-hand column is simply the two added by us. Wiring is extra. Checkatrade allows £400 to £700 for the indoor fused spur and the outdoor isolator, work that must be done or certified by a registered electrician under Part P because it adds a circuit to the house. Sources: Checkatrade; IET.
Why might a Dartford job come to more than that?
- Leasehold. The freeholder of a flat is entitled to recover reasonable costs: a surveyor, a solicitor for the licence to alter, their own administration. If the work touches structure they retain, such as the outside wall or the roof, they may also ask a premium, and no statute caps it. Allow for the paperwork as well as the pipework.
- A new estate. Management companies sometimes dictate a position or a finish, and where the estate's planning permission stripped out permitted development rights, a planning application and its fee are added to the job.
- Height. If the outdoor unit must sit on a flat roof or several storeys from the room, expect extra pipe, a tower or lift hire and possibly a condensate pump.
- Heritage. A flat over a shop, a listed building or a road-facing wall inside one of Dartford's six conservation areas may require an application with drawings.
- Access. A tight side passage or a shared garden slows everything down.
Sources: LEASE; Planning Portal; Dartford Borough Council.
What does an hour of cooling cost in electricity?
Checkatrade's rough guide is 20p to 60p. The arithmetic supports the lower end for a modern unit. The Energy Saving Trust describes typical cooling efficiency as around 7, meaning a unit putting out 2.5kW of cooling takes in about 0.36kW of electricity. At the Ofgem cap of 26.32p per kWh for October to December 2026, holding a room at temperature costs roughly 9.4p an hour. Bringing a baking room down from 30°C costs more, and so does running an old or oversized unit. Sources: Checkatrade; Energy Saving Trust; Ofgem.
And as a heater?
Compared with anything you plug in, remarkably cheap. Running at a seasonal efficiency of 4, the unit turns 26.32p of electricity into four kilowatt-hours of heat, so each one costs about 6.6p; a fan heater or an oil-filled radiator charges the full 26.32p for the same warmth. Mains gas at 7.97p per kWh, before the boiler's own losses, comes much closer, which is why the clearest winners are the 3,830 Dartford homes heated by electricity alone. The heat pump page tabulates all three. Sources: Ofgem; Census 2021.
What are the ongoing costs?
A service once a year, which Checkatrade prices nationally at £70 to £120 per unit. Systems whose refrigerant charge is above the F-gas threshold also need a leak check at least once every 12 months, and it can be done on the same visit. A business whose cooling exceeds 12kW in total has a TM44 energy inspection to arrange at least every five years on top. See servicing. Sources: Checkatrade; GOV.UK; GOV.UK.
Why is the cheapest quote often the dearest?
Because it leaves things out. Before comparing totals, ask each installer:
- Is the capacity identical, and is the unit reversible?
- Are the electrics in the price, and who will sign the Part P certificate?
- How much pipe is included, and what is the rate per extra metre?
- Is a tower or lift allowed for?
- Whose company F-gas certificate does the work fall under?
- Who prepares the noise calculation and handles any consents?
- What conditions are attached to the warranty?
A quote several hundred pounds lower that says nothing about three of those is not the lower quote. How we build ours is explained on our air conditioning in Dartford page.
Questions people ask
What does a portable cost by comparison?
Checkatrade lists a 12,000 BTU portable at £300 to £420. What that saving buys and what it gives up is set out in portable against fixed.
And a unit without an outdoor box?
Checkatrade publishes no figure for monobloc units, so these are priced at the survey. The monobloc guide explains what they are and where they suit.
Is the 26.32p rate fixed?
Only until 31 December 2026. It already reflects the removal of VAT from electricity until 31 March 2027, and Ofgem sets a new cap every quarter. Your tariff may be above or below the cap.
Sources we checked
- Checkatrade: what air conditioning installation costs (May 2026)
- IET: Part P of the Building Regulations for England and Wales
- LEASE: the charges a landlord may make for consent to alterations
- Planning Portal: when an air source heat pump on a house or flats is permitted development
- Dartford Borough Council: the borough's conservation areas
- Energy Saving Trust: an overview of air-to-air heating (slides, 2024)
- Ofgem: price cap unit rates and standing charges, October to December 2026
- Census 2021: type of central heating, Dartford
- GOV.UK: how often F gas equipment must be checked for leaks
- GOV.UK: the guide to air conditioning inspections (TM44)
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
Air conditioning installation
The whole job from the first measurement to the handover of the remote, with every consent checked on the way.
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 servicing
An annual visit for any system by any installer, with the legal leak check where the charge demands one.
Other guides
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.
Portable or fixed air conditioning: which is right for you?
Price, power, noise and running cost, and when a portable is the right call.
Want us to ring you?
A name, a number and a postcode is enough. Say which room if you can. Or ring 01322 952910.