Democratic senator Maria Cantwell of Washington state sponsored the legislation to extend the Clean Energy Treasury Grant Program, or section 1603, to cover projects that start construction by 2012.
Now the grant only covers projects that start construction by the end of 2010 and come online by the end of 2012.
Equivalent to 30% of project costs, the grant is available to developers in lieu of the federal production tax credit (PTC).
Cantwell said: "This bipartisan amendment is fully paid for, and along with a predictable price on carbon, will jumpstart America's urgently needed transition to a cleaner, more diverse 21st century energy economy."
American Wind Energy Association chief executive Denise Bode urged Congress to adopt the measure, writing in a letter with other renewable association leaders: "This program has been extremely successful in both deploying renewable energy projects and creating jobs quickly."
The association chiefs said the amendment's effect would be similar to that of the Renewable Energy Incentive Act, a bill sponsored by Feinstein. However, the bill has been with the Senate finance committee since December.
Cantwell's legislation, co-sponsored by Republican George LeMieux and Democrats Dianne Feinstein, Debbie Stabenow, Robert Menendez, Jeff Merkley and Ben Nelson, has been proposed as an amendment to HR. 4213, the American Jobs and Closing Tax Loopholes Act.