A self-plus-one coverage option won’t be available in the health insurance program for federal employees and retirees until 2016, according to the Office of Personnel Management.

Currently, enrollees in the Federal Employees Health Benefits Program may choose between self-only coverage and self and family coverage. Family coverage rates are substantially more expensive and don’t vary by how many additional persons are insured.

A budget law passed in December approved making a self-plus-one option available to enrollees as soon as 2015. However, a spokesperson said that OPM “expects to implement the self plus one option for the 2016 plan year.”

More than 250 insurance plans participate in the FEHBP, the large majority operating only in local areas. Rates and coverage terms are negotiated annually between the carriers and OPM, a process that starts in the spring and ends with an open season each fall for enrollment decisions for the following year.

The OPM spokesperson said in an e-mail that adding the option will require the insurance carriers, federal payroll systems and the federal retirement system to revamp their processes. “Making this significant change across many systems would need to be completed well before the beginning of the 2015 open season to ensure user testing and quality assurance,” the spokesperson said.

“FEHB carriers will need to submit rate and benefit proposals on the self plus one category. Adding self plus one will require precise actuarial evaluation for the new rates, and agencies will need sufficient time to make changes to their systems to accommodate payroll deductions,” the spokesperson added.

The White House last spring proposed adding that option to the FEHBP program and Congress later approved it in part because the Congressional Budget Office determined it would be a money-saver for the government.

The government pays about 70 percent of the total FEHBP premium cost for enrollees, whether they are in self-only or self and family plans. The CBO projected that premiums for a self-plus-one option would fall between the rates of the two other options and that retirees, especially, would be drawn to it.

However, the CBO also predicted that once a self-plus-one option is added, the family coverage option “would become more costly than under current law because the average number of people covered by policies of that type would rise.”

The idea of adding a self-plus-one option to the FEHBP had been in circulation for many years, advocated mainly by enrollees with only one eligible family member who contend that it is unfair for them to have to pay the same rates as those with multiple eligible family members.

Self-plus-one coverage is available under the separate Federal Dental and Vision Insurance Program. In that program, the second person must be someone who would be eligible under family coverage rules. Domestic partners, for example, are excluded.