Cannot Be Repaired

The simplest situation in which a car may be considered totaled is if it is not possible to repair it at all. If fixing it is not an option, the insurance company will total it.

Too Expensive to Repair

The insurance company may also consider your car totaled if, even though it can be repaired, it would cost the company more to repair it than to replace it. There are several factors that go into this decision.

ACV

In order to measure the value of your car, an insurance company appraiser will determine the ACV, or actual cash value, of the vehicle. This value takes into count the age of the vehicle, any upgrades or prior damage, sales tax, and comparisons with the prices that similar cars are currently selling for.

Costs

Most insurance companies will decide to repair a vehicle if the repairs would cost up to 80 percent of the ACV, but some companies may use lower numbers.

Other Costs

The insurance company also takes any other costs into account when making the decision to total a vehicle. For example, some policies require the company to rent you a vehicle while your car is being repaired. This cost is considered part of the cost of repairing the car.

Source:

Autobodystopshop: When Is A Car Totaled?