Alternative fuels advocates aren’t the only ones looking for guidance from lawmakers on what their future tax treatment might look like. Several energy tax incentives — including the production-tax credit that has helped the wind power industry grow — are scheduled to expire on Dec. 31.

The production tax credit for renewable energy power production has its fair share of vocal boosters and detractors. In January, Congress changed how project developers can claim the credit, allowing them wiggle room to “begin construction” on their facilities by the end of the year, rather than requiring them to start delivering electricity to the grid by the expiration date.

The language change takes some of the pressure off lawmakers to ensure an extension before Jan. 1, though industry observers say a lapse would still curtail the number of wind farms — by far the biggest beneficiary of the production tax credit — built next year.

If history is a guide, Congress will probably extend most of the benefits retroactively at some point in 2014, said KPMG’s John Gimigliano, a former House Ways and Means Committee senior tax counsel.

Regardless, next year “will be a lost year for wind development,” he said. “Even if it’s done retroactively, it’ll have been a lost year.”

Other provisions scheduled to expire by year’s end include:

A tax credit for two- or three-wheeled plug-in electric vehicles.

Income tax credits for biodiesel, renewable diesel fuel and qualified mixtures.

Credits for new construction of energy-efficient homes and for energy-efficient appliances.