Many of the most costly items of optional high-tech equipment available on new prestige cars are worth very little on the used market, according to GlassGuide.co.uk.

In the large luxury car segment, which includes the BMW 7 Series, Audi A8 and Mercedes-Benz S-Class, the average cost of radar cruise control is £1,750.

After 12 months the typical trade value of the system is £250, equivalent to an 86% fall in value. Depreciation for the car itself is slower – over the same period the trade value of a typical diesel-powered car in the segment falls by only 42%.

Other new on-board technologies also depreciate rapidly. The average cost of a night vision system is currently £1,250, but after 12 months its value will have fallen by 80% to just £250.

Often the options that retain their value best, as well as improve the overall saleability of the vehicle, are those that enhance the aesthetic appeal of the car, said Richard Crosthwaite, prestige car editor at GlassGuide.co.uk.

“Investing in a manufacturer-fit styling upgrade is often very worthwhile, as it can return more than 100% of its original cost. For example, a one-year-old BMW 325i with an optional M Sport pack is currently worth £3,500 more than a standard 325i of the same age, even though the pack itself would have added only £2,500 to the list price.”

Crosthwaite added larger wheels can also enhance the desirability and value of a prestige car. “Opting for 20-inch alloy wheels in preference to the standard-fit 19-inch items on a BMW 330i coupe will add £1,000 to the value of a one-year-old example.”

Underlining the fact that used car buyers are not necessarily attracted by the latest high-tech gadgets, Crosthwaite said there has been a sustained improvement in the retained value of sunroofs over recent months. “The trend is most apparent with panoramic sunroofs on large prestige SUVs, where they can retain more than 50 per cent on a one-year-old vehicle.”

Used car buyers have growing expectations about the equipment that will be fitted to a prestige-brand car.

“On larger models, items such as Bluetooth, park distance control and sat nav are increasingly regarded as essential to secure a sale on the used market,” added Crosthwaite. “A large, one-year-old SUV without full-screen satellite navigation would be worth £2,500 less than one fitted with such a system.

“Buyers of smaller prestige cars are still willing to pay extra for such options. A one-year-old Audi A3 or BMW 1 Series specified with park distance control, Bluetooth and a sunroof would currently draw a premium of between £500 and £1,000.”