The priciest ZIP codes for car insurance

If you're wondering why your car insurance rates are through the roof, take a close look at your ZIP code. This five-digit identifier has a dramatic impact on how much you pay, swinging the cost of coverage by hundreds, sometimes even thousands, of dollars.

Indeed, just changing the location of your garage by a few miles makes a massive difference, according to CarInsurance.com, which just completed a study of the impact of ZIP codes on rates.

Consider a Michigan driver who lives in the Detroit area. If he lives in the 48227 ZIP code, just northwest of downtown Detroit, he'd be paying the highest insurance rates in the nation -- an average of $5,109 a year. But if he moved about 10 miles down highway 96 into Livonia (ZIP 48154), his average insurance cost would plunge to just $2,369, a savings of $2,740.

That's for the same coverage for the same driver and same car.

"The average driver is not aware how much location impacts how much they pay for car insurance because there are many factors that go into setting your rate," said Michelle Megna, managing editor of CarInsurance.com. "But a lot of car insurance companies use your ZIP code as a starting point when setting rates, looking at how many claims they get from that ZIP for theft, vandalism, accidents -- and the cost of those claims."

The bottom line: Moving a few miles, often even in the same city, can save or cost you a bundle.

CarInsurance.com looked at 33,410 ZIP codes in the U.S. and calculated rates by surveying the nation's six-largest auto insurers -- Allstate, Farmers, GEICO, Nationwide, Progressive and State Farm -- based on coverage for a single 40-year-old male who commutes 12 miles to work each day, and drives a Honda Accord.

Policy limits were assumed to be 100/300/50 ($100,000 for injury liability for one person, $300,000 for all injuries and $50,000 for property damage in an accident), with $500 deductibles for both collision and comprehensive coverage. This hypothetical driver has a clean record and good credit.

Naturally, individual rates will vary based on the driver, car and coverage. But by holding all those factors constant, CarInsurance.com was able to isolate the impact of ZIP codes on average costs, said Megna. The site also put up a cost-comparison tool, allowing consumers to compare rates in their own ZIP code to the averages in nearby areas.

Michigan, which has a no-fault insurance system, is one of the most costly states to insure a car overall. The national average for insuring this hypothetical driver was $1,231, Megna said. But the cheapest rate in Michigan ran $1,628.

What are the most and least costly ZIP codes?

Most costly:

1. Detroit, Michigan, in ZIP code 48227: $5,109
130 percent over statewide average of $2,226

2. Brooklyn, New York, in ZIP code 11226: $3,877
151 percent increase over statewide average of $1,542

3. Philadelphia, Pennsylvania, in ZIP code 19132: $2,760
128 percent increase over statewide average of $1,210

4. Providence, Rhode Island, in ZIP code 02903: $2,749
38 percent increase over statewide average of $2,000

5. New Orleans, Louisiana, in ZIP code 70117: $2,542
53 percent increase over statewide average of $1,657

6. Los Angeles, California, in ZIP code 90029: $2,416
69 percent increase over statewide average of $1,433

7. Woodbridge, Connecticut, in ZIP code 06525: $2,291
50 percent increase over statewide average of $1,527

8. Baltimore, Maryland, in ZIP code 21216: $2,256
79 percent increase over statewide average of $1,258

9. Miami, Florida, in ZIP code 33142: $2,248
60 percent increase over statewide average of $1,402

10. Royalton, Kentucky, in ZIP code 41464: $2,104
42 percent increase over statewide average of $1,484

The least expensive ZIP codes:

1. Green Springs, Ohio, in ZIP code 44836: $647
16 percent lower than the statewide average of $771

2. Arden, North Carolina, in ZIP code 28704: $671
16 percent lower than the statewide average of $800

3. Saco, Maine, in ZIP code 04072: $709
7 percent less than the statewide average of $763

4. Christiansburg, Virginia, in ZIP code 24073: $751
16 percent less than the statewide average of $899

5. Boise, Idaho, in ZIP code 83706: $753
9 percent lower than the statewide average of $831

6. Lake Havasu City, Arizona, in ZIP code 86403: $769
25 percent lower than the statewide average of $1,021

7. West Lafayette, Indiana, in ZIP code 47907: $770
14 percent lower than the statewide average of $891

8. Allouez, Wisconsin, in ZIP code 54302: $776
15 percent lower than the statewide average of $908

9. Concord, New Hampshire, in ZIP code 03303: $785
9 percent lower than the statewide average of $864

10. Normal, Illinois, in ZIP code 61761: $827
17 percent lower than the statewide average of $1,001