If you're shopping for a new car, chances are you're considering things such as gas mileage, vehicle size, comfort and even that all-important stereo. But have you checked on the cost of insurance?

A quick call to your agent might help you narrow your choices -- and avoid a second case of sticker shock after you drive your new car home.

The reason: Along with your own driving record, your ZIP code, and the demographics of the drivers in your household, the make and model of your vehicle can have a big impact on your insurance bill, says Russ Rader, spokesman for the Insurance Institute for Highway Safety. Of all of those factors, the type of vehicle you put in your garage is the only variable you can change immediately.

"The choice of the car itself is going to affect, in particular, what you will spend for comprehensive and collision," says Jeanne Salvatore, senior vice president of public affairs for the Insurance Information Institute.

That makes shopping around for insurance, as you shop around for that car, a good move. To compare insurance policies and quotes, visit Insureme.com, a Bankrate company.

Why some cost more
Collision damage costs are one of the main factors in differentiating the cost of insuring one type of car over another, says Rader. To a lesser extent, you also want to look at how attractive the car is to thieves.

Vehicles that top the insurance-cost list tend to be either high horsepower, high dollar or expensive to repair, Rader says. An expensive choice:  "Sporty cars that are favored by young drivers who are risky drivers, so they are crashing a lot."

Higher horsepower means the driver is more likely to be going faster and getting into more accidents. That will send insurance rates up for everyone who owns a similar car.

Many of the vehicles that are expensive to insure "share a common problem, and that is horsepower," says Kim Hazelbaker, a senior vice president with the Highway Loss Data Institute.

Size matters
Some think that a smaller, more maneuverable car is able to outrun trouble and avoid crashes. It's a myth, says Rader.

"When you look at the statistics and insurance claims, small sports cars tend to be in more crashes," he says. Adding to the problem: "They tend to be engaged in faster driving."

From a statistical standpoint, the safest models tend to be the full-sized family-sedan-type cars, he says.

A few other special circumstances can also send rates through the roof. If a car is a popular target for thieves, your insurance company might charge you higher rates to keep it covered.

If you're driving a high-priced car, it will likely cost more to fix after a collision. As a result, your insurance bill will go up when you add it to the policy, Rader says. Likewise, some luxury or high-end cars feature aluminum body panels that are more expensive to fix or replace than sheet metal, he says.

One other factor to consider: How much damage is your vehicle likely to inflict in a crash?