Rental car insurance can be an important decision to make in order to cover any damage or medical expenses, but you may already be covered. Your primary car insurance or credit card issuer may provide rental car coverage. Furthermore, rental car insurance offered by rental agencies are typically secondary (or supplemental) to your primary car insurance.
Collision coverage is offered by the rental car company, but this is not insurance per say. At a cost of $14-20 per day, collision coverage will cover only damages to the vehicle. If waived, you are held to the full cost of damages. It can be in your best interest to accept the collision coverage.
Your primary car insurance may cover rentals and should be taken advantage of. Call your insurance agent and check out the perimeters of your existing coverage. Your insurance policy must carry liability and collision coverage. Liability coverage will cover any costs associated with injuring another individual. Be sure to contact your agent prior to renting the car or you may not be covered.
Another option, but limited, is your credit card. Some credit card issuers may offer rental coverage if their card is used to pay for the rental. However, this is usually secondary to your primary coverage and may only cover the collision partition. It is prudent to contact your credit card agency to determine the full extent of coverage.
Rental car insurance offered by the rental agency can be deemed unnecessary as your primary coverage will cover your liability and damages. However, those with no car insurance or wish not to use their own should purchase liability and collision insurance from the rental agency. Be sure to check your current coverage prior to renting, and then assess whether supplement coverage is needed.