By William Opalka

BOSTON — The New England Electricity Restructuring Roundtable met for the 150th time on Wednesday to celebrate some successes and discuss ways to continue moving the nation to a low-carbon future.

The meeting has grown from the small group of stakeholders that met in 1995 in the early days of electric industry restructuring. Last week’s session, organized by Raab Associates, filled a hotel ballroom with about 300 attendees.

Among the successes of the last 20 years: the growth of energy and capacity markets and an increasing reliance on clean energy sources and energy efficiency.

Attendees also expressed disappointment over challenges they thought would now be in the rearview mirror.

“We need to put a meaningful price on carbon. We can’t do anything unless we do that and it has to show up on” bills, said Susan Tierney, senior advisor at Analysis Group.

John Howe, senior advisor to Poseidon Water and former chairman of the Massachusetts Department of Public Utilities, agreed. “The single biggest failure was not to put a price on carbon,” he said.

While New England has cut emissions through the Regional Greenhouse Gas Initiative, the record is mixed.

“RGGI is a signal accomplishment,” said Richard Cowart, director of European programs for the Regulatory Assistance Project. “This is something that will be a lesson for the world — that carbon revenue is just as important as carbon pricing,” because it can be a source of investments to lower carbon emissions through energy efficiency programs and clean energy technologies.

RGGI’s trading prices have been far below EPA’s estimated “social cost of carbon,” however, and revenues from the program have been used to fill state budget shortfalls — not solely to support lower emissions.

Even if prices were higher, RGGI would be only a piecemeal solution, said William Hogan, the Raymond Plank professor of global energy policy at the Harvard Kennedy School.

“The scope of the [climate change] problem is enormous. And it’s worldwide. If you’re not doing it everywhere, you’re wasting your time,” he said. While the recent Paris Agreement shows some global movement, enacting a carbon tax in the U.S. to further its goals is “politically impossible,” he said.

But Hogan sees hope in some movement for more comprehensive tax reform in Washington. “On that day, they’re going to be doing 50 things that are politically impossible, individually, and I want to make sure a carbon tax is one of the 50.”

Despite some frustrations, Peter Fox-Penner, professor in the Questrom School of Management and director of Boston University’s Institute for Sustainable Energy, said there is promise in the future. “New England’s emphasis on renewable energy and energy efficiency shows industry is poised to meet the challenge of decarbonizing the sector while retaining reliability and affordability.”

But the role of natural gas as a “bridge” fuel to that future is a question, as carbon emissions in New England have ceased to fall. The potential loss of the region’s nuclear power fleet also could harm efforts to arrest climate change.

“The dash to gas was appropriate at the time … but the time is at hand to cross that bridge and now is the time to get to cleaner and more sustainable solutions,” Howe said.

But given the low price of gas and wide availability, political and cultural shifts may be needed to resist that temptation.

“The discipline to keep the natural gas in the ground is going to be one of the great challenges of the next generation,” Cowart said.