An alternator replacement at a UK independent costs £250–£550 depending on the car. Small hatchbacks at the low end, longitudinal diesels or anything with the alternator buried under other components at the top. Main dealer £450–£900. Diagnose properly first — half the time the fault is the battery, not the alternator.
Is it the alternator or is it the battery?
The classic mistake: battery warning light on the dash, car won't start next morning, someone says 'alternator's gone' and spends £500 on the wrong part. Real test takes 5 minutes: measure battery voltage with engine off (should be 12.4-12.7V). Start engine, measure again (should be 13.8-14.5V). If it climbs, alternator is charging fine — you have a battery problem, £80-£120 fix. If it stays flat or drops, alternator isn't charging — replacement job. Never spend on an alternator without seeing those two readings. Any indy will do the test for £30 and roll it into the repair if it becomes one.
Why alternator prices vary so wildly
It's access, then output. A small petrol Fiesta with the alternator right on top: £250-£320 fitted with a quality Bosch or Denso rebuilt unit. A Land Rover Discovery 3 with the alternator behind the AC compressor and under the intercooler pipework: £550-£700 because it's 4-5 hours of labour. Output rating matters too — a 90-amp alternator is cheaper than a 180-amp one because there's less copper in it, and modern cars with lots of electronics increasingly need the higher-output units. Fit the correct amp rating for your car; under-spec alternators run hot and fail early.
New vs remanufactured — the honest answer
A 'new' alternator at parts factor prices is usually a rebranded remanufactured unit anyway. A proper remanufactured Bosch or Denso alternator with 2-year warranty performs identically to a factory-new one, costs 30-50% less, and is what most indies fit. Genuine new-new alternators exist at 2× the price and are only worth it on very new cars still under manufacturer warranty. Avoid: unbranded 'new' alternators from marketplace sellers at £80-£100 — they're rebuilds of Chinese units with no quality control and typically fail within 6-12 months.
Warning signs of a failing alternator
Battery warning light glowing dim on the dashboard (not full-bright — that's fuse or wiring). Headlights dim at idle then brighten with revs. Electronic accessories cutting out or resetting (radio, sat-nav, climate). Whining or growling noise from the engine that changes pitch with revs (worn alternator bearing). Battery keeps going flat despite recent replacement. Any two of those together and the alternator is on the way out — book the test.
How long a good alternator should last
A quality OE-fit alternator typically lasts 120,000-180,000 miles or 10-12 years. Getting under 60,000 miles usually means: wrong-spec replacement fitted, chronic battery undercharging (bad earths or wiring), or drive belt tension issues. If a garage has fitted an alternator that failed inside 2 years, ask them for warranty replacement — Bosch and Denso remanufactured units come with 2-year warranty as standard.
Typical UK prices
- Small petrol, easy access: £250 – £340 — Fiesta, Corsa, Yaris — Bosch reman
- Mid-size petrol/diesel: £300 – £450 — Focus, Golf, Astra, Octavia
- Large diesel or awkward access: £450 – £700 — Discovery, Range Rover, BMW N57
- Main dealer any of above: £450 – £900 — Roughly 1.6× indy price
Frequently asked questions
How much does an alternator cost to replace UK?
£250-£550 at an independent for most UK cars. Small petrol at the low end, awkward-access diesel at the high end. Main dealer usually £450-£900.
How do I know if it's the alternator or the battery?
Voltage test with engine running: 13.8-14.5V = alternator charging fine (battery fault). Below 13V = alternator not charging (alternator fault). 5-minute test at any indy.
Can I drive with a failing alternator?
Short journeys yes, on remaining battery capacity — 20-40 miles typical before you run out of volts. Long-term no; you'll flatten the battery and be stranded. Fix inside a week.
Are remanufactured alternators reliable?
Yes if branded (Bosch, Denso, Valeo). Same output specs as new, 2-year warranty typical, 30-50% cheaper. Avoid unbranded reconditioned units — quality varies wildly.
How long should an alternator last?
120,000-180,000 miles or 10-12 years for a quality unit. Earlier failure usually points to wiring or belt-tension issues that need fixing alongside the replacement.