Alternator replacement cost
An alternator replacement typically costs £300–£580 at a UK independent garage, based on the median across more than 900 models in our price database. Small cars sit nearer £250, premium and stop-start cars can push £700+.
What decides the price
Access is everything. On some cars the alternator is 45 minutes at the top of the engine. On others it hides under manifolds or requires removing the front of the car. Stop-start systems use smart, higher-output alternators that cost more as parts and sometimes need coding to the car.
Signs your alternator is going
Battery warning light on while driving, dim lights that brighten with revs, a whining or grinding bearing noise, repeated flat batteries with a battery that tests fine, or electrics dropping out. A garage can confirm it with a charging test in minutes, typically checking for roughly 13.8 to 14.8 volts at idle.
New, recon or used?
Quality reconditioned alternators with a warranty are standard practice and perfectly good. Cheap unbranded new units are a false economy, the diode packs fail early. As with turbos, the labour to do the job twice costs more than the part.
Do not ignore it
Once charging fails you are running on battery alone, which on a modern car means 20 to 40 minutes before everything shuts down, sometimes with the steering getting heavy as systems drop offline. Not one to chance on a motorway.
Common questions
How do I know if it is the battery or the alternator?
A battery that goes flat overnight is usually the battery. A battery that dies while driving, with the red battery light on, is usually charging. Any garage can test both in ten minutes, often free.
Can a flat battery damage the alternator?
Repeatedly jump-starting and forcing the alternator to recharge a dead battery from empty works it hard and can shorten its life. If the battery is old, replace it at the same time.
Why was my quote more than £580?
Usually access (some cars bury the alternator), a smart stop-start unit that costs more and may need coding, or a seized belt tensioner being replaced at the same time, which is often sensible.
How long do alternators last?
Typically 100,000 to 150,000 miles. The bearings and brushes wear, so high-mileage failure is normal wear rather than bad luck.