After weeks of behind-the-scenes talks, Democratic lawmakers on Thursday night finally unveiled the details of the Virginia Clean Economy Act, a 75-page plan to get Virginia to zero carbon by 2050.

The legislation was hailed by its sponsor, Del. Richard “Rip” Sullivan of Fairfax, as a “historic” step on energy policy.

“This is an achievable roadmap,” he told the House Labor and Commerce Committee. “It’s an achievable directive from this General Assembly.”

Democrats agreed, passing the bill along for further consideration on a 13-9 party-line vote that frustrated some backers’ hopes for bipartisan support.

One of this session’s two major vehicles for getting Virginia to zero-carbon emissions, the Clean Economy Act is the product of weeks of negotiation since the initial version was introduced at the start of the session among what Sullivan has called “the widest variety of stakeholders any bill like this has ever seen.”

The consensus that emerged in the substitute bill presented Thursday was slow to form, frustrating many legislators charged with considering a complex law they had not yet seen.

“For three weeks, on all of these bills, I’ve been told that ‘Senator Spruill, we’re right here,’” Democratic Sen. Lionell Spruill of Chesapeake, who chairs the Senate Energy Subcommittee, complained Monday upon receiving news that the substitute had not yet been finalized. “Here we go again.”

But the negotiations also resulted in a bill backed not only by Gov. Ralph Northam’s administration, environmental groups and the renewables industry, but also the state’s two powerful regulated electric monopolies, Dominion Energy and Appalachian Power Company — a coalition that many said was the result of a new political landscape dominated by Democrats less sympathetic to the utilities.

“Politics can change a lot of minds very quickly,” said Harrison Wallace, Virginia director for the Chesapeake Climate Action Network, one of the groups involved in crafting the legislation.

The version presented Thursday hews to the original bill’s four main goals of achieving zero-carbon emissions by 2050, establishing a mandatory renewable portfolio standard, as well as an energy efficiency standard and expanding access to rooftop solar. But timelines and some targets have changed, and exactly how the state will achieve those goals is more clearly sketched out.

Among the top-line goals of the legislation is the mandatory renewable portfolio standard, which dictates that 30 percent of all Virginia’s energy generation must come from renewable sources by 2030, and 100 percent must come from clean energy sources (including nuclear) by 2045 for Dominion and 2050 for APCo.

Other key provisions set binding energy efficiency savings targets, direct Virginia to join the Regional Greenhouse Gas Initiative, establish a schedule for retirement of fossil fuel plants, and expand the net metering cap from 1 percent to 6 percent and the power purchase agreement cap from 50 to 500 megawatts — the latter significant wins for supporters of distributed solar.

Numerous portions of the act have been designed to be compatible with other legislation moving through the General Assembly, including a bill sponsored by Democratic Del. Cliff Hayes of Chesapeake that would declare 5,200 megawatts of offshore wind “in the public interest” — although the legislation omits a heavily criticized part of Hayes’s measure that declares all project costs to be reasonable and prudent.

Unlike the session’s other big energy omnibus, the Virginia Green New Deal sponsored by Democratic Del. Sam Rasoul of Roanoke, the Clean Economy Act would not establish an outright moratorium on new fossil fuel plants but would instead rely on market forces to halt their construction.

Language in the substitute, however, would bar the State Corporation Commission from issuing any new certifications for new facilities until the completion of a state study on achieving zero-carbon emissions and retiring fossil fuel plants. And, on a more permanent basis, it would require the SCC to include the “social cost” of carbon in its consideration of any application to build new generation facilities.

What the legislation means for the two new natural gas plants Dominion has proposed to build in Chesterfield and Pittsylvania is uncertain.

Many Green New Deal supporters, who waved signs in support of that legislation during the Clean Economy Act hearing, remained skeptical of the bill, particularly with the Green New Deal still alive in the House.

Jolene Mafnas of environmental advocacy group Food and Water Action said that the legislation “still does not stop the buildout of fracked gas infrastructure” and criticized its timeline as “unambitious.”

“It does not address the urgency of the climate crisis,” she said.

The Office of the Attorney General and the SCC also expressed concerns about the potential cost of a 5,200-megawatt offshore wind buildout to ratepayers, with the SCC estimating it could add $13 per month to customers’ bills.

The presentation prompted a pointed question from Del. Mike Mullin, D-Newport News: “Has there been a projection of the cost of not doing anything?”

Still, some lawmakers remained concerned; Del. Kathy Byron, R-Bedford, said it was “questionable” whether the legislation’s provisions were “sufficient for ratepayer protection or not.”

The Clean Economy Act will now move to the House floor. An exact version of the House legislation will be taken up by the Senate Commerce and Labor Committee at a meeting Sunday.