Air conditioning is generally reliable, but when a unit stops cooling, starts dripping water or refuses to switch on, the first question is always the same: what is this going to cost? Here are honest ballpark figures, plus the one piece of advice that could save you paying for the same repair twice.
Typical repair costs at a glance
Most engineers charge a call-out or diagnosis fee first, often somewhere around £60–120, and many will knock it off the bill if you go ahead with the repair. Ask before they come out. From there, the cost depends on what has actually failed.
| Repair | Rough cost (parts and labour) |
|---|---|
| Call-out / diagnosis | £60–120 |
| Capacitor replacement | £100–200 |
| Temperature sensor / thermistor | £80–200 |
| Drainage fault (blocked condensate line or pump) | £75–250 |
| Fan motor (indoor or outdoor) | £150–450 |
| Refrigerant leak find, repair and regas | £200–600+ |
| PCB (circuit board) replacement | £200–600 |
These are rough ranges, not quotes — always get a price for your actual fault before agreeing to work. Costs swing with the brand (some manufacturers charge a lot for parts), the age of the unit, and where you live, with London and the South East usually at the top end. A capacitor is a cheap part and a quick job; a PCB on an older or obscure unit can be slow to source, and is sometimes the point where replacement starts to make more sense.
The regas trap: a top-up usually means a leak
This is the bit most price guides skip, and it is the most useful thing on this page. An air conditioner is a sealed circuit — refrigerant does not get "used up" like petrol. If your system is low on gas, the gas went somewhere, which almost always means a leak.
A cheap regas that ignores this is not a repair; it is a deposit on the next one. The new refrigerant escapes through the same hole, you are back to warm air within months, and you have paid twice. Refrigerant is also a potent greenhouse gas, which is why a reputable engineer will not simply top up a system that is known to be leaking without investigating.
A good engineer will find the leak first — typically with a pressure test, an electronic detector or UV dye — repair it, then vacuum the system and recharge it. That is why an honest price for "a regas" is higher than the cheapest figures you might see advertised: the top-up itself is the cheap part, and the leak detection is what you are really paying for. If an engineer offers to gas it up without mentioning leaks at all, treat that as a red flag.
Who is allowed to do the work
Anyone handling refrigerant in the UK must be F-Gas certified — it is a legal requirement, not a nice-to-have. Ask for the certification before letting someone open the sealed circuit. Electrical repairs like capacitors and PCBs do not touch the refrigerant, so F-Gas is not strictly required for those, but you still want someone who works on air conditioning day in, day out rather than a general handyman. Our repairs page covers what to expect from a proper repair visit.
What you can safely check yourself
Before you pay a call-out fee, check the free stuff: dirty filters cause a surprising share of "broken" air conditioners, as do tripped breakers and flat remote batteries. Clean or rinse the filters (your manual shows how — it is usually a clip-out job), make sure the outdoor unit is not choked with leaves or hemmed in, check the fuse board, and try new batteries in the remote.
That is where safe DIY ends. Never remove the casing from the indoor or outdoor unit — there are components inside that can hold a charge even with the power off — and never attempt anything involving the refrigerant pipework. Anything beyond filters, batteries and the fuse board is a job for an engineer, and anything touching refrigerant legally requires an F-Gas certified one. An annual service also catches small problems — slow leaks, blocked drains, tired parts — before they become the expensive rows in the table above.
Repair or replace?
A rough rule that serves most people well: if the unit is under ten years old and the repair costs less than about a third of a new system, repair it. Above that, think hard about replacing.
- Age. Split systems commonly last somewhere in the region of 10–15 years. Spending £500 on a 13-year-old system rarely pays off, because the next fault is usually not far behind.
- R22 systems. If your system is old enough to run on R22 refrigerant — broadly, systems installed in the early 2000s or before — it cannot legally be regassed, as R22 has been banned from servicing use for years. Any refrigerant fault on an R22 system effectively means replacement.
- The maths. A new single-room split typically costs somewhere in the £1,500–3,000 range fitted — our installation cost guide has the full picture. A modern unit is also a reversible heat pump, so it heats efficiently in winter as well as cooling in summer, and newer models tend to be cheaper to run — see our running costs guide.
Where it gets marginal — say a £450 fan motor on a nine-year-old unit — ask the engineer what else is likely to go. An honest one will tell you.
Finding someone you can trust
The hard part of AC repair is not the price — it is finding an engineer who will look for the leak instead of just selling you gas. If you would rather not ring around, tell us what is wrong and we will match you with a vetted, F-Gas certified local engineer — start here. No obligation, and no call centre passing your number to five firms at once.