The cost of car insurance for teen drivers is pretty steep. On average, 18-year-olds pay 18 percent more for car insurance if they sign up for an individual policy as opposed to remaining on their parents' policies, according to a new report.

Is your teen driver on your car insurance policy? (Catherine Yeulet, ThinkStock)

In New Jersey, 18-year-olds add an average of 68 percent to their parents' car insurance bills, and it costs 19 percent more than that for them to get their own auto insurance in the Garden State. So, staying on their parents' policy is the better deal.

According to the report, In Rhode Island, 18-year-olds pay an average of 53 percent more for individual coverage. In Connecticut, they pay 47 percent more. In Oregon, it's 47 percent more, Nevada is 41 percent more and Maine is 40 percent more. Hawaii does not allow auto insurance companies to factor age or length of driving experience into their costs while insurers in Illinois, Alaska and Florida only charge 18-year-olds an average of seven percent more for individual coverage.

"In most states, individual policies significantly add to the already high cost of insuring a teen driver," said Laura Adams, senior analyst. "Young people are not getting some of the advantages that mom and dad are like having a long, clean driving record, good credit or multiple vehicles. It is expensive to add a teen driver. There is no getting around that, but we are finding that it's a little less expensive to be on mom and dad's plan."

Acording to Adams, the congestion on New Jersey roads along with the high number of accidents tends to drive up insurance rates.

"The good news is that it does get less expensive each birthday the teen has. As they're getting older, statistically they are becoming a different profile of driver," Adams said.

Across the country, individual policies cost nine percent more than family coverage at age 19 and 4 percent more at age 24. Even at the age of 24, there are states, including North Carolina and Maryland, where individual coverage costs significantly more than family coverage.