5 best and worst states for car insurance costs

The summer driving season is fast approaching, which is great news if you're planning a road trip. But summer is also the busiest season when it comes to auto insurance claims, so now might be a good time to make sure that your coverage is up to date. According to the National Association of Insurance Commissioners (NAIC), the average annual cost of car insurance nationwide was $815 in 2012.

At the same time, insurance premiums fluctuate widely by state, due to factors such as rural vs. urban drivers, percentage of uninsured drivers, local cost-of-living figures and hazardous weather conditions.

To get a closer look at state-by-state insurance costs, InsuranceQuotes.com has just issued a report measuring average premiums using information from the largest insurance carriers in each state. It also created an "average" driver: someone who is employed and who drives a 2012 sedan, has a bachelor's degree, an excellent credit score and no lapse in insurance coverage.

With those factors in mind, here are America's five most and least expensive states for car insurance.

Most expensive: #5 Louisiana

Insurance premiums for drivers residing in the Bayou State are 33 percent above the national average. Much of Louisiana is rural, which means lower crime rates, fewer cars, less congestion and fewer accidents. But Mike Barry, a spokesman with the nonprofit Insurance Information Institute, pointed out that the state ranks high when to comes to natural disasters like hurricanes, which can damage vehicles through flooding, falling trees or debris thrown by high winds.

Most expensive: #4 Delaware

Delaware residents have auto insurance premiums that cost 41 percent above the national average. CarInsurance.com points out that he state has low liability requirements for personal, bodily injury and property damage insurance. It's also near the bottom of the national list when it comes to auto thefts by state.

But Delaware has a relatively dense population. It's also in close proximity to two of the worst cities in the nation when it comes to auto crash rates: Washington, D.C., and Baltimore, Maryland -- which might also play a factor.

Most expensive: #3 New York

The Empire State's auto insurance premium rates are 42 percent above the national average. The metro New York City region has some of the highest population densities in the nation, so it's no surprise it also has high rates of auto theft and collisions. Residents of New York City's borough of Brooklyn have the second-highest car insurance premiums in the nation (Detroit is first). In fact, residents of one particular Brooklyn ZIP code pay 151 percent more than the average premium payment elsewhere in the state.

But some other factors may be at play. The Insurance Information Institute's Mike Barry said Metro New York is still dealing with the aftermath of Superstorm Sandy in 2012, "and the claims made on flooded vehicles could still be affecting prices today."

Most expensive: #2 Rhode Island

It may be the smallest state, but Rhode Island has some of the biggest auto insurance premium costs in the nation. They're 45 percent above the national average. The state capital of Providence is one of the top cities in the nation when it comes to auto collision rates. And about 15 percent of the cars on Rhode Island's roads are uninsured, driving up rates for people who do have insurance.

Most expensive: #1 Michigan

What's up with Michigan? The average annual cost for an auto insurance policy in the state is an astounding 136 percent above the national average.

According to InsuranceQuotes.com, a couple of factors are involved.

"Michigan is the only state where car insurance includes unlimited lifetime personal injury protection, so that's a major reason why car insurance is so expensive in Michigan," Laura Adams, the company's senior analyst, said in a press statement.

"Since younger people are injured more frequently in auto accidents than older drivers, the cost of covering a lifetime of medical expenses could easily climb into the millions-of-dollars range," added Lori Conarton, communications director for the Insurance Institute of Michigan.

Another issue is the unusually high number of Michigan drivers without insurance. InsuranceQuotes.com said some estimates say around half of the drivers in Wayne County, where Detroit is located, don't have auto insurance. No surprise, then, that coverage in Wayne County costs 45 percent more than Michigan's statewide average.

Least expensive: #5 Wisconsin

Being a mostly rural state means fewer cars and less traffic, and that has helped Wisconsin keep its auto insurance costs 28 percent below the national average. While rates in the state's biggest city, Milwaukee, are the state's most expensive and nearly twice what most Wisconsin drivers pay, the state capital of Madison is one of the best cities in the country when it comes to low auto collision rates.

Least expensive: #4 Maine

Maine's relatively small and mostly rural population allows auto insurers to keep costs 33 percent below the national average

"We have few large urban areas so we have lower overall traffic problems, and we don't have hailstorms or tornadoes," Jeffrey McDonnell, president of the Maine Insurance Agents Association, recently told Insure.com. McDonnell also noted that Maine has one of the highest rates of insured drivers in the U.S., "so we have more people sharing the risk."

Maine was recently listed as the least expensive state when it came to insuring 2015 editions of the top 20 best-selling vehicles. The state also has one of the lowest motor vehicle theft rates in the U.S.

Least expensive: #3 Ohio

Being a partially rural state is just one factor that has helped keep Ohio auto insurance rates 33 percent below the national average. But intense competition among the state's insurance companies is certainly another. Insure.com, quoting state data, says over 670 auto insurance carriers do business in the state, which is second only to Illinois.

"Ohio continues to be a strong advocate for its citizens and has a strong insurance department that stays on the forefront as times are changing," Jeannine Giesler, president of the Professional Independent Agents Association of Ohio, told the website. "It's possible to get from independent agents rates that are very competitive."

Least Expensive #2: Idaho

With its car insurance rates 37 percent below the national average, Idaho has the least expensive car insurance in the Western U.S. A recent Insure.com study said the average premium in Idaho is about half of what a driver would pay in Montana and several hundred dollars lower than the average rate in Oregon.

Being a mostly rural state certainly keeps down those auto insurance rates. However, Insure.com also noted that only about 7 percent of Idaho drivers are uninsured, compared to the national average of around 13 percent.

Least expensive: #1 North Carolina

Leading the list with the least expensive car insurance in the nation, North Carolina has premium costs 41 percent below the national average. The Tar Heel State has some obvious advantages.

As InsuranceQuotes.com points out, it's mostly rural. But as North Carolina's insurance commissioner says on the state's Department of Insurance website, the state also "sets a cap on car insurance rates, and insurance companies compete by offering discounts below the established cap."

In fact, the competition to sell insurance for the lowest auto premiums is intense. According to InsuranceQuotes, North Carolina insurers offer more than 2,000 different types of auto insurance discounts, "an uncharacteristically high number."