DAVE GRAM, Associated Press

MONTPELIER -- The Vermont House voted overwhelmingly Wednesday to sharply expand a 16-year-old program that allows electric customers to generate their own electricity, ship it to the power company and roll back their monthly bills, sometimes to zero.

The bill would allow "net metering" for self-generating customers to expand nearly four-fold. Current law requires utilities to accept customer-generated electricity up to an amount equaling 4 percent of their peak capacity but the bill up for final House approval on Thursday would boost that cap to 15 percent.

The bill would also allow utilities to petition state regulators for still higher caps.

At the end of 2016, when federal tax credits for generation by utility customers expire, the state program would as well. The second half of the bill advanced Wednesday on a 136-8 roll call vote calls on the state Public Service Board to draft recommendations for how net metering would be handled after that, and submit those recommendations to the Legislature for approval.

As a lobbyist on energy issues before being elected to the House in 2002, Rep. Tony Klein, D-East Montpelier, the chairman of the House Natural Resources and Energy Committee, said he pushed for creation of the net metering program as a way to promote renewable energy and reduce carbon emissions tied to generating the energy used in Vermont.

Klein said the solar industry has really taken off in Vermont since the state adopted a requirement in 2011 that utilities pay customers an equivalent of 20 cents per kilowatt-hour for the solar energy they generate. That’s above the approximately 14 cents utilities charge at retail, Klein said. But he said solar energy’s value rises well above 20 cents per kwh on the hottest days in summer, when utilities must pay $1 or more per kwh at wholesale.

"It’s now not uncommon to see solar in the state of Vermont that is a direct result of the statutes that you all have been part of furthering," Klein said.

Critics of the program said they worried that when customers with solar power installations lower their power bills to zero, that leaves the rest of the company’s customers to cover costs ranging from the company’s billing and other back-office operations, to the crews who repair fallen power lines in storms.

But backers countered that by reducing peak power demand, Vermont had been able to avoid costly new construction of power lines and infrastructure, meaning the solar boom was saving the overall system money.