Open enrollment in Affordable Care Act (ACA) health insurance policies sold on government marketplaces begins Nov. 1, but consumers will face a 25-percent jump in premiums on the popular silver plans at HealthCare.gov, the Wall Street Journal reports in today’s edition.

Administration officials caution, however, that up to three-quarters of enrollees will qualify for federal subsidies, lowering their monthly premiums below $100 from the projected $302 average.

The rise in premiums comes as health insurers flee the government market due to exploding costs as the older and sicker flock to the policies while the younger and healthier stay home — and uninsured.

As a result, one in five consumers in the 39 states covered by HealthCare.gov will find a choice of just one insurer in their area, reflecting the loss of participant companies.

Because some 2016 policies are lapsing due to insurer flight, consumers who need to find replacement  policies will have until Dec. 31 to enroll for coverage beginning Jan. 1, 2017. Those without canceled policies must enroll by Dec. 15 for Jan. 1 coverage.

Those with lapsing Obamacare policies overall will have until March 1 to find a replacement policy, according to guidelines issued by the Centers for Medicare and Medicaid (CMS), which administers the marketplaces. Others will have only until Jan. 31.

However, enrolling after Dec. 31 to replace a canceled policy will result in a lapse in coverage.