How much does it cost to change a lightbulb? Up to £846.

A blown headlight bulb can cost up to £846 to replace on some of Britain’s best-selling small cars, new research reveals.

A study into 13 popular models on sale today by What Car? found headlight repair bills vary by several hundred pounds depending on whether the models have halogen or HID or LED bulbs. Of the vehicles examined, four came with High Intensity Discharge (HID) bulbs on some or all trim levels and three had LED bulbs.

HID and LED bulbs are far brighter than halogen lights and can last up to 10 times as long, but replacements can cost close to £1,000. The complexity of HID and LED bulbs is partly to blame for the higher costs but in many instances manufacturers have also switched to sealed headlight designs, which cannot be opened up like a normal unit to allow for bulb replacement. As a result, customers have to buy a complete headlight unit to fix a blown bulb.

The cost of replacing a traditional halogen bulb on a Volkswagen Polo costs owners just £18. However, buyers who choose the high-spec GTI model face a £846 repair bill for the car’s LED sealed headlight unit.

Similarly, Suzuki Swift owners with SZ3 or SZT trim levels only have to pay £4 to replace a blown bulb, while those with a high-spec Swift SZ5 will have to pay £684 for a replacement HID unit.

Even if the headlight unit isn’t sealed, HID bulbs are still far more expensive to replace than normal halogen items. The HID bulb for a Vauxhall Corsa Elite costs £317, while a halogen bulb for a lower spec version is just £17. Audi A1 SE trim owners will pay £18 for a new halogen bulb, but those with S-Line Nav models have to pay £211 for a new HID bulb and control unit.

Claire Evans, What Car? consumer editor, said: “The longevity of HID bulbs makes them a viable option on a new car. However, if you are buying a used car as a second household vehicle or as a first car for a son or daughter, you – and they – could be landed with a massive repair bill for a blown bulb that could even render the car a write-off due to it being uneconomical to repair.”

Greg Whitaker, editor of What Car?’s sister title Car and Accessory Trader expects replacement costs of headlight units will fall in the future as the aftermarket sector catches up to the technology: “It’s happened in the past with a number of car parts. The floating speedometer needle in the Mercedes C-Class was prone to breaking and AC Tronics created a fix for this. And the ECU in the Vauxhall Meriva had some fragile components that frequently broke, so a fix for this was also created.”

The full report is available in the December issue of What Car? which is on sale now.

Cost comparison: New headlight bulbs for small cars