Updated April 7 at 5:16 p.m.

Transportation, energy and the construction fields feature as primary focus areas in a bill Senate Democrats rolled out Thursday to accelerate decarbonization efforts amidst what lawmakers called a sluggish approach by state agencies.

The policy-heavy, $250 million bill set to hit the Senate floor next week (S 2819) would combine an overhaul of the offshore wind procurement process with new investments in electric vehicle infrastructure, incentives to encourage more drivers to go electric, greater scrutiny on the future of natural gas, and local options to restrict the use of fossil fuels in building projects.

Senators pitched the proposal as a needed follow-up to the law Gov. Charlie Baker signed last year, which committed Massachusetts to achieving net-zero carbon emissions by 2050, a target that will require major changes throughout the economy.

Where the 2021 law "was and is about laying benchmarks," the new bill "is about doing what needs to be done to hit those benchmarks," said Telecommunications, Utilities and Energy Committee Co-chair Sen. Michael Barrett.

The bill would use $100 million to create a Clean Energy Investment Fund, allocate $100 million to incentivize adoption of electric vehicles, and deploy $50 million to build out electric vehicle charging infrastructure.

Senate Ways and Means Committee Chair Michael Rodrigues said the legislation would use surplus state tax revenues to seed that spending, though he said lawmakers could opt to add to the trust funds in the future using federal aid or other sources.

"It's not one and done on these issues," he said.

The sectors targeted in the bill play major roles in existing carbon production. Transportation accounts for the largest share of the Bay State's greenhouse gas emissions, representing about 42 percent, while electricity consumption represents 19 percent and building consumption represents 32 percent, according to a December 2020 state report.

Senate President Karen Spilka said those three areas "really need significant attention if we are to meet our ambitious goals of having net-zero emissions by 2050."

"Let's face it: improvements we make in education or health care policy won't mean anything if our coastal cities and our cities are underwater," Spilka said while unveiling the bill, flanked by about a dozen other senators. "This is the most important issue of our time."

The Senate teed up the bill, its version of an offshore wind bill the House approved last month (H 4524), to be considered on Thursday, April 14. Amendments will be due by 4 p.m. on Monday.

On the transportation front, the Senate bill aims to accelerate a statewide embrace of electric vehicles. It would require rebates through the Massachusetts Offers Rebates for Electric Vehicles (MOR-EV) program to be offered at the point of sale, making the benefits available to motorists immediately, and increase the rebate amount in most cases by $1,000 to $3,500.

Motorists could receive an additional $1,000, representing a rebate of $4,500, if they trade in a combustion engine vehicle when purchasing an electric car or truck.

"We wanted to make sure in the bill that we are not stimulating the purchase of electric vehicles by single car owners at the expense of people who live in cities and who may not be able to afford a car or may rely primarily on mass transit," Barrett, a Lexington Democrat, said. "If you add what we do with what the feds are supposed to do, you could be bringing down the cost of a $40,000 EV to $27,500."

Starting in the year 2035, all new vehicles sold in Massachusetts would need to produce zero emissions, a change that Barrett said would align the Bay State with New York and California. The Baker administration has proposed a similar cutoff of the sale of fossil fuel vehicles, which would be codified into state law under the Senate bill, as part of its 2050 decarbonization plan.

All buses purchased and leased by the MBTA would need to be zero-emissions vehicles starting in 2028, and the entire fleet -- which today includes more than 1,000 buses -- would need to be zero-emission by 2040.

Utilities would need to offer reduced electricity rates for off-peak electric vehicle charging, and new developments would need to allocate 10 percent of their parking spaces to EV charging, proposals that feature alongside the bill's $50 million fund to expand charging infrastructure.

Taking aim at an industry that both Baker and the House have already targeted with legislation, the Senate's wide-reaching energy and emissions proposal would update the process for procuring new offshore wind developments to supplement the in-development Vineyard Wind and Mayflower Wind.

Senators proposed keeping a price cap in place for new bids, a contrast from Baker's proposal to eliminate the cap and the House-approved bill that would remove it in most situations, but would allow some economic development costs to be excluded from the calculation. The Senate legislation would require the total cost of a bid to be less than 10 percent higher than the most recent offshore wind procurement.

It would also instruct the state Department of Energy Resources to choose a winning bid in consultation with an independent evaluator, removing utilities from that part of the equation, and would reduce the remuneration for utilities to 1.25 percent. Senators said that piece would save ratepayers money.

Other clean energy sources feature in the Senate bill, too. The legislation would allow nuclear fusion, networked geothermal and other new technologies to be eligible for support from the Massachusetts Clean Energy Center and would greenlight agricultural and horticultural land to be used as solar panel sites, so long as the panels do not impede existing uses.

With some lawmakers frustrated that the Baker administration's stretch code would not authorize cities and towns to mandate builders use all-electric heating, the Senate bill calls for launching a "demonstration project" in which 10 municipalities could limit the use of fossil fuels in new construction.

A key motivating factor, senators said, is the pace of work underway in executive offices and state agencies and lawmakers' desire to enshrine their recommended approach in law. Gov. Baker oversees the state's energy and environmental agencies and is scheduled to leave office early next year when his successor takes over.

Referencing the role of natural gas and the municipal stretch energy code as pressure points, Sen. Cynthia Creem said some "specific agencies are not really helping us achieve the emissions (reductions) we need."

"I don't think it's a 'this administration versus another' problem, but we're seeing that unless we move quickly, we're not going to meet the emissions (reductions) that were required and the agencies, we don't think, are taking the quick approach that they should be taking," Creem, a Newton Democrat, said.

After he and Creem earlier this week voiced concerns with the utility-driven Future of Gas report, Barrett said Thursday that natural gas on any given day accounts for roughly 65 percent of the state's electric power generation at once.

"The future of gas is the ballgame, in many respects, and it must not be a process that ends with a governor who's decided to leave," Barrett said. "What we're doing here is keeping the process open. We're giving this governor ample opportunity to have input, but we're keeping the process open for the next governor as well and making sure that things don't come to a premature conclusion."

The breadth of the Senate's proposal could put it at odds with the House, whose leaders have already secured passage of a narrower offshore wind procurement reform bill that did not feature major action aimed at transportation, solar energy, building or other components senators proposed.

Lawmakers had to approve their 2021 climate bill a second time to secure its signature into law after their slow pace of negotiation took the gubernatorial amendment process off the table and drew a veto of the first version.

And with each branch eyeing a different scope of energy industry action so far, finding consensus in the slightly less than four months remaining for formal lawmaking business could prove challenging.

Asked if she is concerned about reconciling the divergent House-Senate approaches, Spilka said she "tend(s) to be an optimistic type of person, glass half full."

"I believe that the House also recognizes that climate is an existential threat to our planet, and we need to take action," Spilka said. "The last bill we did, we both mentioned that this is not the last bill that we will be doing on climate. I believe that we'll, you know, work this through like we do with the other issues we have."

Baker's offshore wind bill also diverges from the Senate approach, calling for $750 million in American Rescue Plan Act funding to launch a clean energy investment fund.

Pete Wilson, a senior advisor to the advocacy group Transportation for Massachusetts, praised senators for focusing on emissions from the transportation sector while calling for more substantial action to decrease the state's reliance on motor vehicles.

"We appreciate the Senate's goal of decarbonizing our vehicle fleets and the investments included in the bill to get us there. But with the average age of cars currently on the road being more than 12 years, and electric vehicles remaining out of reach to low-income people even with increased incentives, we must seek more comprehensive transportation solutions," Wilson said in a statement. "We look forward to working with the Senate to include additional provisions that shift Massachusetts from our car-centric culture by promoting public transit, walking, and biking. Doing so will not only lower emissions from transportation, but improve public health, fight traffic, and benefit quality of life for all."

This story was updated to include additional details about the proposal.