A series of proposals in both the House and Senate tax overhaul bills would pummel the renewable-energy and electric-vehicle industries.

Legislators from both chambers are now hashing out their differences in the reconciliation committee in hopes of delivering a final bill to the White House before the end of the year. Clean-energy lobbyists are scrambling to push back on provisions they and others fear could stunt development or deployment of technologies needed to lower the nation’s greenhouse-gas emissions.

“It’s headed backwards at a very crucial time, because things are just taking off,” says Tom Turrentine, director of the Plug-In Hybrid and Electric Vehicle Research Center at the University of California, Davis.

Observers do say that some of the most damaging measures could be removed during reconciliation, in part because several seem to have been the unintentional consequences of rushed-through changes.

The Senate’s Tax Cuts and Jobs Act, passed in the early morning last Saturday with handwritten scribbles down the margins, contains at least two major provisions stirring anxieties at renewable-energy companies.

One measure, designed to prevent companies from moving money overseas to reduce tax obligations, could make it far more difficult to fund renewable-energy projects.