When you shop for car insurance, you’re driving blind. Give your details to a dozen carriers and you could end up with a dozen different quotes, some twice as high as others.

Insurers base their premiums on many factors, including age, driving record, and car type. But when Consumer Reports analyzed more than 2.7 billion premiums—the bulk of the U.S. auto insurance market—we also identified some factors that you might not even be aware of, including credit history and education, that have nothing to do with your driving. We also learned that because each insurer has its own pricing formula—penalizing or rewarding factors differently—consumers can save by shopping around.

It worked for Donna Greene of Greenburgh, N.Y., a Geico customer for more than 20 years. She saved $793 on auto coverage and $390 on homeowners by moving to Amica, an insurer based in Rhode Island. “Don’t assume that because you’ve been a good customer for years, you’re getting a break,” she says. “Insurers take advantage of your inertia.”

Poor Credit Makes Rates Skyrocket
A two-car couple with poor credit will pay an extra $2,090, on average, compared to a family with excellent credit. That’s more than what it usually costs to add a teen driver or even the penalty for having two DWIs.

CR’s advice: Shop around. For example, an Illinois driver with poor credit could save about $1,700 by using Country Insurance vs. Metropolitan. Also, improve your credit by paying credit card bills on time and monitoring your record for errors and fraud. For free copies of your reports, go to annualcreditreport.com. (California, Hawaii, and Massachusetts forbid insurers from using credit scores when setting rates.)

Accident Not Your Fault? It Will Still Cost You
A two-car family with just one not-at-fault accident within a three-year period typically pays about $270 more each year. And if you are responsible, the penalty can be more than twice as high.

CR’s advice: Comparison shopping can yield big savings. In Pennsylvania, a driver with one at-fault accident with Allstate can save more than $1,050 by signing up with Erie Insurance Group, Nationwide, or State Farm. In New York, a driver with one moving violation can save about $800 with Progressive, compared with Liberty Mutual.

how to save on car insurance
Infographic: Nicolas Rapp

How We Did Our Price Analysis

For our analysis of car insurance premiums, we first created profiles of 44 hypothetical policyholders ages 20 to 80. They included men and women, singles and married couples, and families with and without teens. They all had perfect driving records, excellent credit histories, and 2016 Toyota Camry LEs. They also had identical liability, collision, comprehensive, and other insurance coverages.

We then used data from Quadrant Information Services, a company that collects insurers’ pricing formulas, to get annual quotes for our policyholders from the largest company in each state and Washington, D.C.—specifically, each insurer’s largest subsidiary, where available.

Finally, we changed the driver’s characteristics to see how premiums changed. For example, we looked at what the average premium would be if the driver had an at-fault accident or bought a home.

When a company did not change its rate due to a particular characteristic, its premium was not included in our analysis. When appropriate, we used a subset of our drivers. For instance, we looked only at drivers ages 60 to 80 when evaluating the impact of mature driver education discounts.

Our analysis did not include two insurers in our car insurance ratings: USAA Group, because it’s only open to active and honorably discharged military and their eligible family members; and Amica Mutual Insurance, because it did not provide its data to Quadrant.

Editor's Note: This article also appeared in the March 2017 issue of Consumer Reports magazine.