Before you've even made it to the slopes, prepare to be floored by the £400 extra costs when you pick up your hire car this New Year.

A medium compact car hired from Budget in Geneva costs £398 for a week's New Year hire (27 Jan to 3 Jan), and then drivers are faced with an avalanche of costs at the rental desk totalling £417 i.e., £114 for excess car hire insurance (to protect a customer against the first part of any insurance claim), £76 for an extra driver, £45 for a roof rack, a child's car seat for £51 and a sat nav hire for £131.

iCarhireinsurance.com, the leading provider of stand-alone car hire excess insurance, researched the costs of five rental companies in seven European ski gateways (i.e., Geneva, Grenoble, Innsbruck, Barcelona, Turin, Sophia and Inverness) for a week's hire from 27 December 2014 to 3 January 2015.

Cheapest for car hire: Sophia is the cheapest place to hire a car costing on average only £160 for the week, but ‘extras’ at the rental desk will double this. For example, hiring from Budget, the car hire excess insurance is £40, an extra driver costs £20, a roof rack costs £20, a child’s car seat is £20, and a sat nav is £46 - adding £146 to the original hire cost of £113.

The same pattern can be seen in the other destinations. The average price of car hire costs £409 in Geneva, £397 in Turin, £287 in Grenoble, £255 in Innsbruck, £243 in Inverness and £232 in Barcelona. Whilst the average cost of extras are £344 in Geneva, £405 in Turin, £265 in Grenoble, £248 in Innsbruck, £325 in Inverness and £351 in Barcelona.

Winter Tyres & Snow Chains: Rental companies often levy a ‘winterisation charge’ covering these during the winter period, costing up to £114 in Geneva with Avis. The average 'winterisation' fee across the seven destinations was over £40.

The onus is on the driver, not the hire company, to know the rules and regulations of the country they’re hiring in. For example, police roadblocks near to ski resorts are common in the Alps and police will refuse entry to a car without chains if it's a 'snow chain' compulsory area. A fine may also have to be paid.

Extra Drivers: Often a necessity for a ski group, the most expensive place to pay for an extra driver was Inverness, where travellers would pay around £75 for each extra driver, rising to £252 with Sixt for a driver under 25 yrs. Bulgaria and Innsbruck are the cheapest places with an extra driver adding around £30 to the final bill. Expect to pay around the £50 or the £120 mark (if it's a young driver).

Car Hire Excess Insurance: When driving in wintery conditions it pays to get adequate car hire excess insurance, otherwise any claim up to the excess amount is the driver's responsibility, which can be as high as £1800, for instance, in Turin. Buying this from the rental company instead of in advance from a specialist provider, like iCarhireinsurance.com, is expensive.

On average this excess or waiver insurance will add almost £100 to a hirer's bill if bought from the rental desk. Hertz charges over £150 in Turin and Barcelona for this insurance, which at £19 a day is six times more costly than a £2.99 daily policy from iCarhireinsurance.com.

An iCarhireinsurance.com excess policy also includes vulnerable parts of the vehicle, like the tyres and windscreen, which are sometimes excluded from rental company policies. For example hiring from Budget in Barcelona, its excess insurance costs £91 and an additional policy to cover tyres and windscreen excess is £31 - a total of £122, which is over five times an iCarhireinsurance.com week's policy costing £24 for the week.

Roof Racks: An essential piece of kit for many skiers. Budget for around £30 for a roof rack, although Barcelona was more expensive with an average cost of around £55.

Sat Navs: The most expensive place to hire a sat nav is Geneva where two companies charge over £100 (Budget [£131] and Avis [£110]). Across all locations the average charge was still a hefty £75 so remember to take your own or buy one.

Child's Seat: Expect to pay at least £50 for a child's car seat although this could be over £100 from three rental companies in Turin, which is the most expensive location to rent a car seat. Take your own and put it in the hold.

Rental companies can take the piste for winter car hirers, said Ernesto Suarez, founder and CEO of iCarhireinsurance.com. The avalanche of costs at the rental desk is overwhelming for even the savviest traveller. To keep costs low research the country you're going to and know their winter driving rules. Also bring what you can from home, including a sat nav and child's seat plus a stand-alone car hire excess insurance, to make picking up your hire car as smooth as the nursery slopes.