Revealed: the modifications that will up your car insurance bills

Car insurance

Your motor insurer will charge sky-high premiums if you do anything to increase your car's performance and aesthetics, according to a new study.

Research from MoneySupermarket reveals that some car modifications can almost double your car insurance premiums, while not telling your insurer about even minor changes to a car's spec could invalidate your policy.

On average, motorists pay £423 a year for their car insurance but turbocharging a car can see insurance premium rise by a whopping 93% (or £393). Meanwhile, modifying the gear box will result in insurance premiums going up by almost half (48 per cent) and retuning your engine will see a 23% hike in your insurance bill.

Changes to a car's good looks can also cost you dearly: upgrading wheel arches will add 42% to your premiums, while smartening up the interior of your car with new seats or a steering wheel will see an 18% hike in premiums.

While men are more likely to spruce up a car's performance, perhaps modifying the brakes or adding a turbocharger or air filters, women put safety first, which can cut premiums. Adding parking sensors, for example, can cut your insurance bill by 11%, while adding a security tow bar will cut costs by 6%.

Compare car insurance quotes from more than 130 insurers

Voiding your cover

Kevin Pratt, insurance expert at MoneySuperMarket, said: "When you modify your car in any way, you change its original specification. Your insurance is based on that spec, so the insurer needs to know about the changes, preferably before they are made. It might mean a higher premium but the alternative is to risk voiding your cover, which would leave you uninsured. That would mean breaking the law and, of course, not having any prospect of a payout if you had to make a claim.

"If you're planning to modify your car, ring your insurer before you get the work done and factor any premium increase into the cost of the work. Don't wait until your policy comes up for renewal. If something were to happen in the interim, the consequences could be extremely serious, especially if you are in an accident in which others are injured or killed where you are found liable to pay damages."

More about