InsureMyRentalCar.com compared the cost of extras purchased at a car rental desk with its own costs to encourage customers to go through a third party.

According to its research – which was conducted for a rental for May 26 to May 30 from five rental companies (Alamo, Enterprise, Hertz, Avis and Dollar) in Chicago, Los Angeles, Seattle, Dallas, Denver, New York and Orlando – there is a $157 difference when it comes to the Loss Damage Waiver (LDW) and Collision Damage Waiver (CDW).

The website offers the waivers from $5 per day, $17.50 per trip or $93.99 for an annual policy. The LDW policies offer coverage of up to $100,000; can be purchased from six months to one day in advance; and cover rental car use at home and overseas.

The website also found that Denver is the cheapest place to rent a car (Dollar charges $200 for the week, including service fees and taxes), and the most expensive place is New York where a week's rental with Hertz costs $836.