Typically, you will be entitled to a rental car while your car is being repaired if the at-fault party's insurance policy terms allow for it. When this is done you are being compensated for the loss of your vehicle during the reasonable time in which it takes to repair your car.

In California, if you were using your insurance policy to cover the car's damages you would have had to purchase rental vehicle coverage in order to receive a rental car during the time of the repair. With this type of coverage policy limits vary, the insurance carrier usually pays up to a specified amount per day for a specified number of days. The coverage ends when your vehicle is repaired, the loss is paid, or after the specified period, whichever comes first.

To find out if the responsible person's insurance policy has a provision for a rental car allowance, speak with the claims adjuster on your case. If you feel that they should pay for a rental car but do not you can contact the CA Department of Insurance consumer division.