WASHINGTON - Consumers avoided $3.9 billion in health premium increases in 2012 partly because of the Affordable Care Act's limits on what insurers can charge, the government said Thursday.

About $500 million in excess premiums will be rebated to 8.5 million people this year, while the rest of money is reflected as "upfront value" in the plans, the Health and Human Services Department said Thursday in a statement. Last year's savings are more than triple the $1.1 billion from 2011.

The 2010 health law, an attempt by President Obama to make medical coverage more widely available and affordable, forbids most insurance plans from keeping more than 20 percent of premiums charged for profit and overhead. A report earlier this week showed that other provisions in the law penalizing hospitals for excessive readmissions and encouraging employers to offer wellness programs are slowing the growth of medical costs for insurers, which may explain the latest reimbursements.

"The health-care law is providing consumers value for their premium dollars and ensuring the money they pay every month to insurance companies goes toward patient care," the U.S. health secretary, Kathleen Sebelius, said in the statement.

Exceeding the 20 percent threshold requires companies to reimburse customers through rebates or reductions in future premiums. The insurance industry has said that the Obama administration's focus on premiums masks the true cause of health cost inflation: prices charged by hospitals and doctors.

The rule, which governs a metric known as the medical loss ratio, "does nothing to address the main drivers of health-care costs and puts an arbitrary cap on what health plans spend on a variety of programs and services that improve the quality and safety of patient care," Clare Krusing, a spokeswoman for America's Health Insurance Plans, the industry's Washington-based lobbying group, said in an email.