Hiring a car with Avis this Easter in Larnaca, Cyprus, a holidaymaker will have to book without knowing the price of four of the six main extras they may need to purchase at the rental desk as they are not available on the rental company website during the booking process.

Hire car drivers can be hit with an additional £366* on average of extra costs at the rental desk, often doubling, and sometimes tripling the cost of the hire car. For example the average cost of hiring a car in Tenerife is £141, but the average cost of 'extras' is £347, tripling the overall cost.

This fog of transparency when booking hire cars is highlighted in a new study by iCarhireinsurance.com, the leading provider of standalone car hire excess insurance, which researched six of the main car hire extras (i.e. car hire excess insurance / excess waiver protection, tyre and windscreen excess, child car seats, sat navs, extra drivers and young drivers) at five destinations (Barcelona, Milan, Nice, Tenerife and Larnaca) from five rental companies (Hertz, Sixt, Avis, Europcar and Budget) for the Easter week, 4 - 11 April 2015.

Larnaca was found to be the least transparent place, with only one provider, Sixt, showing the price of all extras online in advance. Extras on Larnaca cost on average £206, almost doubling the average car hire cost of £129*. Hiring with Avis in Larnaca, for instance, customers would only know, in advance, the price of hiring a car seat and the price for a young driver. All other extras' costs are only available at the location*. Tenerife is the next worst offender, again with only one provider revealing the price of all extras online in advance. Barcelona is the most transparent place with Sixt, Budget and Europcar quoting for all extras at this location.

Only Europcar allow customers to book and pay for all extras in advance at all locations except Larnaca. All other providers require some extras to be paid for at the rental desk, meaning that even though a quote has been given, drivers are vulnerable to exchange rate fluctuations.

The study found wide variations in the cost of extras with car hire excess insurance costing between £26 and £171, Tyre and Windscreen excess between £16 and £37, Child Car seats between £19 and £130, Sat Navs between £34 and £87, extra drivers between £18 and £75, and young drivers between £30 and £193, highlighting the importance of knowing the price of these in advance.

Ernesto Suarez, founder and CEO of iCarhireinsurance.com said: “This total lack of transparency on the cost of hire car extras makes hiring a car a minefield for holidaymakers. They may believe they have got a brilliant deal on their hire car only to be landed with expensive extras at the rental desk. One of the most expensive extras is the cost of excess insurance, and tyre and windscreen cover at the rental desk. Drivers can protect themselves from this by purchasing a policy in advance from a standalone provider like iCarhireinsurance.com from only £2.99 a day or £39.99 for an annual policy.”

The amount of the six main hire car extras that can be quoted for in advance and the amount that can be paid for

* Hiring a family car from the 4th - 11th April direct through the rental company website.

Research carried out on the 10th February 2015.