How much does an alternator replacement cost?
A replacement alternator in the UK usually costs between £250 and £800 fitted, and the RAC's own mobile mechanic data puts the average at £513. Most ordinary cars land between about £420 and £530, because the part is the bulk of the bill and it costs much the same wherever you live. Get the charging system tested before any part is ordered, and do not wait for the MOT to flag it, because the test does not check charging at all.
The alternator is the part that keeps your car's electrical system alive while the engine is running. Turn the key and the battery gets you started, but from that moment on the alternator takes over, topping the battery back up and powering everything from the headlights to the heated seats. When it fails, the whole car slowly runs out of electricity. If it turns out to be the battery rather than the alternator, what a new car battery costs is the cheaper answer.
It is not a part most drivers think about until it goes wrong, and when it does the question is always the same: how much to fix it? Below is a realistic picture of UK costs, built on the RAC's published quote data rather than guesswork, along with the warning signs that tell you the alternator, rather than the battery, is to blame. One thing to know up front, because almost nobody mentions it: the MOT does not test the charging system at all, so a car can pass its test and leave you stranded a fortnight later.
What an alternator replacement costs in the UK
The RAC puts it plainly in its alternator guide, published on 30 July 2026: drivers in the UK "can expect to pay anywhere from £250 to £800" for a replacement alternator, and more where the failure has damaged something around it or the car is a premium model.
That is a wide range, so the averages are more useful. The RAC quotes two figures from its own mobile mechanics, and they measure slightly different things, so it is worth keeping them apart rather than blending them into one number.
| RAC figure | Amount | What it measures |
|---|---|---|
| Typical range | £250 to £800 | What UK drivers can expect to pay for a replacement |
| Average replacement | £513 | RAC Mobile Mechanics prices quoted 1 October to 31 December 2025 |
| Average repair | £458 | RAC Mobile Mechanics prices quoted 1 January to 31 March 2025 |
| Diagnostic check | £99 | RAC's own price for up to 30 minutes of fault finding |
So the honest headline is this: most alternator jobs land between roughly £420 and £530, the £250 floor belongs to small, easy cars, and the £800 ceiling belongs to premium models or a job that has turned awkward. Those national quotes come from a single nationwide service, so a local independent may quote quite differently, which is the whole reason to get more than one price. You can compare local garages here and ask each one for a charging test before any part is ordered.
What it costs by car make
Cost follows the car more than anything else. The table below is the RAC's own quote data for its mobile mechanics, gathered between 1 January and 31 March 2025.
| Make | Average alternator price |
|---|---|
| Toyota | £417 |
| Ford | £435 |
| Vauxhall | £436 |
| Citroen | £445 |
| Volkswagen | £466 |
| Peugeot | £469 |
| Renault | £477 |
| Nissan | £478 |
| BMW | £495 |
| Mercedes-Benz | £525 |
Look at the spread rather than the individual rows. From the cheapest make on the list to the dearest is £108, about a quarter more, not the three times difference the £250 to £800 headline suggests. Even a Mercedes-Benz averages £525. If you drive an ordinary car and you have been quoted £800, the make is not the explanation, so ask what else is on the bill.
Where you live barely changes it
Most cost guides tell you labour is dearer in London and the South East. For this particular job, the RAC's own regional quote data says otherwise, and it is worth seeing.
| Location | Average alternator price |
|---|---|
| Sheffield | £422 |
| Medway | £424 |
| Birmingham | £438 |
| London | £443 |
| Coventry | £455 |
| Leicester | £460 |
| Reading | £471 |
| Stoke on Trent | £501 |
| Cardiff | £504 |
| Bristol | £507 |
London sits fourth cheapest of the ten, below Coventry and Stoke on Trent, and £64 below Bristol at the top. The whole spread is £85, roughly 20%, and it does not run north to south in the way people expect. The reason is that an alternator bill is mostly the part, and a part costs the same in Sheffield as it does in Southwark. Labour rates move the total far less here than on a job that ties up a ramp for a day.
The practical takeaway is that shopping around within your own town is worth more than worrying about your postcode. Two garages a mile apart can be further apart on price than two cities.
What the alternator actually does
Think of the battery as a short-term store and the alternator as the charger. As the engine turns, it drives the alternator by a belt, and the alternator generates electricity to run the car and refill the battery at the same time. The RAC describes its three jobs as charging the battery, powering the electrical systems while the engine is on, and regulating voltage so the electronics are not damaged.
If it stops doing that, the car is left drawing on a battery that never gets topped up, and once that is empty the engine cuts out. This is why a failing alternator so often gets mistaken for a dead battery. The battery is the thing that goes flat, but the alternator is the reason it stayed flat.
Signs of a failing alternator
Alternators usually give you some warning. The RAC lists the common ones, and they match what garages see every week.
The battery or charging warning light. A battery-shaped symbol on the dashboard while the engine is running is the clearest single sign that the charging system is not doing its job. It does not always mean the battery, despite the shape. Our guide to dashboard warning lights explains what the colour of the symbol is telling you.
Dimming or flickering lights. Headlights that fade at idle and brighten as you rev, or dashboard lights that flicker, suggest the alternator is struggling to keep up.
A battery that keeps going flat. If you have replaced the battery or jump started the car only for it to die again, the alternator may not be recharging it.
Electrical gremlins. Slow windows, seats that work intermittently or a weak-sounding stereo all point at a charging system that cannot supply everything at once.
Noise, then smell, then silence. The RAC describes a sequence worth taking seriously: a loud grinding noise at speed, which can be followed by a smell of burning rubber and the engine stalling unexpectedly. That is the belt or the bearing going, and it is the point at which the car is about to stop rather than the point at which you book it in.
Is it the battery or the alternator?
This is the question worth answering before you spend anything, because the two faults feel almost identical from the driver's seat and the parts are very different amounts of money. The pattern below is what a garage uses to tell them apart in a couple of minutes.
| What you notice | Points to the battery | Points to the alternator |
|---|---|---|
| When it fails | Struggles to start, especially first thing or in cold weather | Cuts out or dies while you are driving |
| After a jump start | Runs fine and keeps running | Runs, then dies again soon after the leads come off |
| Warning light | Usually nothing until it will not start | Battery symbol lit while the engine is running |
| Lights | Normal once running | Dim at idle, brighten when you rev |
| Age | Battery is more than about four years old | Battery is newish and has already gone flat again |
| Noise | None | Whine or grind from the front of the engine |
If the symptoms sit on the battery side, read our guide to car battery warning signs, which covers what a replacement battery costs. If they sit on the alternator side, get the charging system tested rather than buying a battery you may not need. A proper diagnostic check is cheap next to the wrong part, and the RAC's own diagnostic price of £99 for the first half hour is a fair benchmark for what to expect. Many independents charge less, and some fold it into the repair if you go ahead.
If you are stuck on a driveway right now, our guide on how to jump start a car will get you moving, but treat it as a lift to the garage rather than a fix.
Repair, recondition or replace?
Replacing the whole unit is not the only option, and a good garage will tell you so. The RAC confirms that an alternator "can often be repaired, depending on the type and extent of the damage": worn or noisy bearings can be replaced, damaged or frayed wiring can sometimes be repaired without replacing the whole unit, and in some cases clearing out dirt and debris is enough to restore normal function. Some alternators can also be rebuilt by replacing the internal components.
The RAC's own conclusion is the honest one: "In most cases, it may be more cost-effective to replace the alternator." Repair makes most sense when the fault is clearly mechanical and external, like a bearing or a chafed wire. Once the voltage regulator or the internals are involved, the labour to strip and rebuild starts to approach the cost of a new unit, and you are left with an older part.
If you are offered a reconditioned or pattern unit to save money, that can be a sensible choice, but ask two questions. What is the guarantee, and is it OEM standard? The RAC's own replacements are OEM standard with a 12-month guarantee, so use that as the yardstick when you compare a cheaper quote. A unit that fails again in eight months costs you the labour twice.
What makes an alternator fail?
Alternators are hard-wearing and many last the life of the car. The RAC lists five things that bring them down early:
Wear and tear. The internal bearing spins constantly, and the brushes and voltage regulator wear too. This is the ordinary end of an alternator's life.
Heat damage. The alternator lives in a hot engine bay, and too much heat breaks down its internals.
Electrical issues. Bad wiring or poor connectors can cause the failure rather than result from it, which is why a competent garage tests the whole charging circuit and not just the alternator.
Fluid leaks. Oil or coolant reaching the alternator will damage it. If you have a known leak, fixing it protects the part you have just paid for.
Overloading. Running a lot of extra electronics puts sustained strain on the charging system.
To that list, add the drive belt. A slipping or perished belt stops the alternator spinning properly, so it should be checked at the same time. It is worth being clear that this is the auxiliary belt on the outside of the engine, not the cambelt inside it, which is a separate job on a separate schedule and covered in our guide on when to change your cambelt.
Why the MOT will not catch it
This is the part most cost guides leave out, and it matters more than the price. No part of the MOT tests your alternator or your charging system.
Section 4 of the DVSA inspection manual, the section that covers electrical equipment, lists what the tester must inspect: headlamps, position lamps, stop lamps, direction indicators and hazard warning lamps, fog lamps, reversing lamps, rear registration plate lamps, rear reflectors, the trailer electrical socket, electrical wiring and the battery. The alternator does not appear, and neither does charging output.
The warning lights are no help either. The manual requires the tester to inspect only four "tell-tales": headlamp main beam, direction indicators, hazard warning lamps and rear fog lamps. The battery and charging light is not one of them. A car with a charging light glowing on the dashboard can pass its MOT on those grounds.
What the MOT does check nearby is the wiring and the battery itself, and these are worth knowing because they show up on advisories after a charging fault has been left too long.
| Defect | MOT category |
|---|---|
| Electrical wiring insecure or inadequately secured | Minor |
| Wiring insecure and in contact with sharp edges, or connectors likely to become disconnected | Major |
| Wiring slightly deteriorated | Minor |
| Wiring so damaged or deteriorated it is likely to cause a short circuit | Major |
| Wiring insulation damaged or deteriorated | Minor |
| Wiring insulation heavily deteriorated | Major |
| Wiring insulation in such a condition there is an imminent risk of fire or sparks | Dangerous |
| Wiring likely to touch hot or rotating parts, or drag on the ground | Dangerous |
| Battery insecure but not likely to fall from its carrier | Minor |
| Battery insecure and likely to fall from its carrier or cause a short circuit | Major |
| Battery leaking | Major |
So a fresh MOT pass tells you nothing about your alternator. If the charging light has been on, book a charging test rather than waiting for the test certificate to expire. Our guide to what is checked in an MOT test sets out the full scope, and you can check when your MOT is due in seconds.
What waiting actually costs
An alternator fault does not stay still. It gets more expensive in steps, and each step is avoidable.
| Stage | What is happening | Rough cost |
|---|---|---|
| Charging light comes on, car still drives | Charging output dropping, battery still holding | Diagnostic from about £99, then the repair |
| Battery flattened repeatedly | Deep discharge damages a healthy battery | Alternator plus a replacement battery you did not need |
| Car cuts out on the road | Battery exhausted, engine stops | Recovery on top, and a car parked wherever it stopped |
| Belt or bearing lets go | Grinding, burning smell, belt failure | Damage to what the belt also drives, so the bill grows past the alternator |
The cheap version of this repair is the one you book while the car still starts. The expensive version is the one that starts with a recovery truck.
What should be on the quote
Ask for the quote in writing and check it covers the following:
A charging test, not a guess. The garage should confirm the alternator is at fault before ordering the part, and tell you the voltage it measured.
The battery's condition too. A battery that has been flattened repeatedly may be finished. Better to know now than to fit a new alternator and still have a car that will not start.
The part, named. New, reconditioned or pattern, with the guarantee written down. OEM standard with 12 months is the benchmark.
The drive belt. If it is coming off anyway, ask whether it needs replacing while access is easy.
Labour hours and the hourly rate. This is where quotes diverge most, because an alternator buried behind the engine takes hours that a front-mounted one does not.
If you are weighing a franchise dealer against a local independent, our comparison of a main dealer against an independent garage covers what each is better at. And if you are unsure who to trust with the job, start with our guide on how to choose a good garage.
Hybrids and electric cars
If you drive a fully electric car, this repair is not on your list. There is no engine turning a belt, so there is no belt-driven alternator to replace. What an EV does still have is a conventional 12 volt battery: the RAC confirms that "most electric cars will use a 12-volt battery to power important systems", and when that battery goes flat the car can be as immobile as any petrol hatchback.
That 12 volt battery is still inspected at the MOT. The DVSA manual is explicit that testers "must inspect the battery(ies) on all vehicles including electric and hybrid vehicles", with the same insecure and leaking defects that apply to any car. Propulsion batteries are assessed visually only, and a leaking one means the tester refuses the test outright rather than failing it.
Hybrids sit in between. Many still have a petrol engine and a conventional charging arrangement, so an alternator quote can be genuine. The point to hold on to is simply this: on a full EV, a quote headed "alternator replacement" deserves a question before it deserves a payment.
Is it worth fixing?
For almost any car you plan to keep, yes. A car will not run reliably without a working charging system, and the fault will not clear on its own. The only time to pause is on a very old, low-value car where the fitted cost approaches what the car is worth, and even then it is usually still cheaper than replacing the car.
The sensible sequence is short. Get the charging system tested, get the fault confirmed in writing, get a second quote if the first is at the top of the range, and ask about the guarantee on the part. Regular servicing helps too, since the belt, battery and charging circuit all get looked at, which is covered in our guide on how often you should service your car and in our car service cost guide.
The bottom line
Expect roughly £250 to £800, with most jobs landing near the RAC's £513 average for a replacement. Your make matters a little, your postcode matters less than you think, and the biggest variable is how quickly you act. Book the charging test while the car still starts, get the fault confirmed before a part is ordered, and compare two quotes rather than one.
Prices change and every car is different, so use these ranges to sense-check a quote rather than as a fixed figure. When you are ready, compare local garages and send a booking request, with no payment taken on the site.
Key takeaways
- Expect roughly £250 to £800 fitted. The RAC's average across its mobile mechanics is £513.
- The make matters less than the headline range suggests: Toyota £417 to Mercedes-Benz £525 in the RAC's data, a spread of only £108.
- Your postcode matters even less. London averages £443, below Bristol at £507 and Stoke on Trent at £501.
- No part of the MOT tests the alternator or the charging system, so a fresh pass proves nothing here.
- The battery warning light is not one of the four tell-tales an MOT tester has to inspect.
- A flat battery that keeps coming back is often the alternator, not the battery itself.
- The classic tell is a jump start that works, then dies again once the leads come off.
- An alternator can sometimes be repaired rather than replaced, but the RAC says replacing is usually more cost effective.
- Ask for a charging test and the measured voltage before any part is ordered.
- Waiting turns a £500 repair into a recovery, a wrecked battery and a bigger bill.
Frequently asked questions
How much does it cost to replace an alternator in the UK?
Between about £250 and £800 fitted. The RAC's own mobile mechanic quote data puts the average replacement at £513, and most ordinary cars land between roughly £420 and £530. The part is usually the larger share of the bill, and labour depends almost entirely on how easy the alternator is to reach on your engine.
Is it the alternator or the battery?
They cause similar symptoms. A car that struggles to start but runs fine once going points to the battery. A car that dies while driving, or dies again shortly after a jump start, points to the alternator. A battery symbol lit on the dashboard while the engine is running is the clearest alternator sign. A garage can test both in minutes.
Will a failing alternator fail the MOT?
No. The MOT does not test the alternator or the charging system at all. The DVSA inspection manual covers lamps, wiring and the battery under electrical equipment, and the alternator is not on that list. The battery warning light is not one of the four tell-tales a tester has to inspect either, so a car can pass with the charging light glowing.
Can I keep driving with a failing alternator?
Only briefly, and it is risky. Once the alternator stops charging, the car runs on the battery alone and will eventually cut out, often with no warning. If the charging light is on, drive somewhere safe or call for help rather than pressing on. Repeatedly flattening the battery can also ruin a perfectly good battery.
Can an alternator be repaired instead of replaced?
Sometimes. The RAC confirms worn bearings can be replaced, frayed wiring can sometimes be repaired, and clearing dirt and debris occasionally restores normal function. Some units can be rebuilt. In most cases, though, the RAC says replacing the alternator is more cost effective, because stripping and rebuilding one approaches the cost of a new part.
Is a reconditioned alternator worth it?
It can be, provided the guarantee is written down. Use the RAC's own standard as the yardstick: OEM standard parts with a 12-month guarantee. A cheaper unit that fails again inside a year costs you the fitting labour twice, which wipes out the saving.
Does an electric car have an alternator?
No, because there is no engine turning a belt. An EV does still have a conventional 12 volt battery for its onboard systems, and that battery is inspected at the MOT like any other. If you drive a full EV and receive a quote for alternator replacement, question it before you pay it.
Why do alternators fail?
The RAC lists five causes: ordinary wear and tear on the bearings and internals, heat damage in the engine bay, electrical faults in the wiring or connectors, oil or coolant leaks reaching the unit, and overloading it with too many electronics. A slipping or perished drive belt will also stop it charging properly, so the belt is worth checking at the same time.
How long does an alternator replacement take?
It depends entirely on where the alternator sits. On some engines it is at the front and swapped in about an hour. On others it is buried behind or beneath other components and freeing it takes several hours. That is why labour, not the part, is what makes two quotes for the same car diverge.
Should I replace the battery at the same time?
Ask the garage to test it rather than replacing it automatically. A battery that has been flattened repeatedly by a failing alternator may be damaged, and fitting a new alternator to a dead battery leaves you with a car that still will not start. A test costs almost nothing next to a battery you did not need.