Environmental advocates filled the basement of the State House Tuesday to voice support for a bill that would establish a price for carbon emissions in Massachusetts.

A standing-room-only crowd listened to hours of testimony from economists, business leaders and advocates, who told a legislative committee that putting a price on carbon emissions was the best way to combat climate change.

That’s what state Sen. Mike Barrett’s bill would do — charge $10 per ton of carbon emissions, increasing by $5 per year until reaching $40 per ton. The money raised would be returned to Massachusetts residents as an annual $225 rebate. Electric plants would be exempted from the law, since they’re already part of a cap-and-trade program.

Experts who testified at the hearing said the Commonwealth won’t reach its goal of reducing emissions 80 percent by 2050 without putting a price on carbon emissions.

Julie Fox Gorte of the American Sustainable Business Council says a clear price on emissions will help businesses adjust to climate change.

"A carbon price would help give us a more certain landscape that we could plan on and make investments on the basis of,” she said.

The Massachusetts Energy Marketers Association opposes the bill, saying it's unnecessary because the industry has already taken aggressive action to reduce emissions. Michael Ferrante, who represents the heating oil industry for the Massachusetts Energy Marketers Association, says the bill is confusing and unnecessary, because carbon emissions are already going down.

"Trying to determine the carbon intensity of all the fuel that are cited in the bill is a monumental task — and then to try to rebate consumers is almost ludicrous," Ferrante said. "I don’t see how that can work."