WASHINGTON (AP) — Letting young adults stay on their parents’ health insurance until they turn 26 will nudge premiums nearly 1 percent higher for employer plans, the government said in an estimate released Monday.

The coverage requirement, effective starting later this year, is one of the most anticipated early benefits of President Barack Obama’s new health care law. Many insurers have already started offering extended coverage to families who purchase their coverage directly. And employers say parents have flooded their benefits departments with questions.

The Health and Human Services Department released estimates of the costs and benefits of the requirement as part of a regulation directing employers and insurers how to carry it out.

The new benefit will cost $3,380 for each dependent, raising premiums by 0.7 percent in 2011 for employer plans, according to the department’s mid-range estimate. Some 1.2 million young adults are expected to sign up, more than half of whom would have been uninsured.

Extended coverage will be required starting this fall, for health plan years beginning on or after Sept. 23.