Pima County switched its employee health-insurance program to a self-insured model Tuesday, as a way to save money.

The Board of Supervisors unanimously approved the change, with Aetna Life Insurance Co. hired to administer the plan, the county announced in a press release.

Exact savings weren't announced, but the press release said the $46 million annual cost for health insurance was expected to rise 1.8 percent in the next fiscal year, or $800,000. That compares with an increase of 18 percent, or $7 million, for the current fiscal year.

Until now, the county has contracted with a private insurance carrier, allowing it to assume all the risks and rewards of insuring county workers. The company made money if it kept medical costs below premium payment totals.

Health care costs are consistently falling below premium costs, so the county will reap the benefits by going to self-insurance, the press release said.

The county has about 6,400 insurance-eligible employees, and about 5,300 of them are on health plans along with more than 6,500 dependents.