How much does an alternator replacement cost?

UK alternator replacement costs at a glance

Prices include parts and labour. Typical market observations as of 2025. Always get a current quote.

Getting two or three quotes can save £50 to £150 on this repair. Labour rates and parts sourcing vary significantly between garages.

Average alternator replacement prices by UK city

Typical range at an independent garage for a mid-size car, parts and labour included.

Prices are approximate market observations as of 2025. Always get a current quote.

What the alternator does and why it fails

What it does

The alternator is a generator driven by the engine via the serpentine belt. It produces electrical current to power everything on the car and to keep the battery charged while you drive. Without a working alternator, the battery will drain and the car will eventually stop.

Age and mileage

Most alternators last 80,000 to 150,000 miles. High mileage vehicles will eventually need the alternator replaced as internal brushes and bearings wear out. The built-in voltage regulator can also fail independently of the main windings.

Serpentine belt failure

A snapped or slipping serpentine belt will prevent the alternator from spinning, causing immediate battery drain and a warning light. Always check the belt condition when diagnosing a charging fault.

Wiring faults

Corroded or damaged wiring between the alternator and battery can cause intermittent charging faults that look like alternator failure. A proper charging system test will identify a wiring fault before you pay for a new alternator unnecessarily.

How to get a fair price for an alternator replacement

1. 1. Ask the garage to perform a charging system test before quoting for parts. A test costs £20 to £40 and confirms whether the alternator, battery, or wiring is at fault.
2. 2. Confirm whether a new or reconditioned alternator is quoted. Both are acceptable; make sure the reconditioned unit comes with a 12-month warranty.
3. 3. Ask whether the serpentine belt will be replaced at the same time. It is good value to do so if the belt has high mileage.
4. 4. Get at least two quotes, particularly if your first quote is from a dealership.
5. 5. Check whether the quote includes any diagnostic work already carried out or whether that is charged separately.

AutoFixFair lets you post your alternator job once and receive competing quotes from local garages in Manchester, London, Birmingham, and other UK cities.

Common questions about alternator replacement costs

What are the signs of a failing alternator?

The most common warning signs are a battery warning light on the dashboard (often shaped like a battery even though the alternator is the cause), dimming headlights that get brighter when you rev the engine, electrical accessories such as heated seats or the radio cutting out intermittently, and a whining or grinding noise from the engine bay. In advanced cases the battery will drain completely overnight and the car will not start. If your battery keeps going flat and is relatively new, have the charging system tested before replacing the battery.

How do I know if it is the alternator or the battery that has failed?

A good garage will perform a charging system test, which takes about ten minutes. The test checks the battery voltage at rest (should be 12.4 to 12.7 V), the charging voltage at idle (should be 13.5 to 14.7 V), and the load capacity of both components. If the alternator is not holding 13.5 V or above at idle, the alternator is the problem. If the battery cannot hold charge despite a healthy alternator output, the battery needs replacing. These are two different faults with different repair costs.

Can I drive with a failing alternator?

For a very short distance in an emergency, yes. Once the alternator stops charging, the car runs purely off the battery. A fully charged battery will typically power the car for 20 to 30 minutes of driving before it is exhausted and the engine cuts out. Do not use major electrical loads such as headlights, heating, or wipers for longer than necessary. Get the car to a garage or pull over and wait for recovery rather than risk being stranded on a busy road.

Should I fit a new or reconditioned alternator?

A reconditioned (remanufactured) alternator is a cost-effective option and commonly used by independent garages. A reputable unit that has been professionally reconditioned to OE specification will typically carry a 12-month warranty and last as long as a new part. The saving over a new unit is typically 30 to 50 percent. Avoid very cheap alternators from unknown suppliers: the quality of remanufacturing varies significantly and a failed alternator shortly after replacement will cost you a second labour charge.

Is the serpentine belt replaced at the same time as the alternator?

It is strongly advisable to replace the serpentine belt (also called the auxiliary drive belt) at the same time as the alternator, especially if the belt has more than 50,000 miles on it. The belt drives the alternator and removing it is part of the job on most vehicles. Fitting a new belt while the system is already apart adds minimal time and typically costs £20 to £40 extra. Failing to replace a worn belt means a higher chance of it snapping shortly after the new alternator is fitted.

How long does an alternator replacement take?

Most alternator replacements take one to two hours at a garage. On straightforward cars the alternator is easy to access and the job is under an hour. On some vehicles, particularly those with complex engine bay layouts or where the alternator is located behind other components, the job can take up to three hours. Ask the garage to confirm the expected time before you book so there are no surprises on the labour charge.

What affects the cost of an alternator replacement?

The main factors are: the make and model of your car (parts costs and access time vary widely); whether a new or reconditioned alternator is fitted; whether the serpentine belt is replaced at the same time; your location (London and the South East are typically more expensive); and whether you use an independent garage or a franchised dealer. Independent garages consistently charge less than dealers for this repair with no difference in quality when using the same parts.

Will a faulty alternator cause an MOT failure?

Not directly, but an alternator that causes the battery warning light to illuminate will be noted by the tester and the light alone is an MOT advisory if it relates to a non-safety system. More importantly, a flat battery caused by a failing alternator could prevent the car from starting for the MOT at all. If your charging system warning light is on, get it fixed before your MOT appointment.

How long should a replacement alternator last?

A quality alternator, new or properly reconditioned, should last 80,000 to 150,000 miles under normal driving conditions. Alternators are typically replaced only once in a car's life on vehicles that do not exceed 100,000 miles. Factors that shorten alternator life include excessive short journeys (which keep the alternator under constant heavy load charging the battery), high electrical loads from aftermarket accessories, and heat soak from a poorly ventilated engine bay.