Stacey Vanek Smith: A major government incentive for solar power expired this week.

But as Eve Troeh reports from the Marketplace sustainability desk, renewable energy is set to grow in 2012.

Eve Troeh: The past three years, solar power projects were essentially 30 percent off, thanks to a U.S. Treasury grant program.

Rhone Resch at the Solar Energy Industry Alliance says most grants went to the little guys.

Rhone Resch: Small electricians or small developers that install solar on homes and businesses.

But that grant just expired. Now, it’s a tax rebate. Resch says small firms won’t owe enough in taxes to benefit, and could close. But big solar companies will use that tax break. They’re luring big, new investors.

Resch: Bank of America, Google, Berkshire Hathaway. They feel comfortable not only with the technology but with the returns on their investment.

Solar looks sweet to investors as more utilities promise to buy the power, says Tim Kemper. He follows energy finance for the Resnick Group.

Tim Kemper: Really what’s driven it is the capital, without a doubt.

That goes for wind power, too. A different tax credit has spurred investment in wind turbine factories. Bruce Hamilton at Navigant Consulting says that expires in a year.

Bruce Hamilton: Therefore, the developers are rushing to get projects in before that deadline.

Because there’s no telling how the political winds might blow for renewable energy beyond 2012.

I’m Eve Troeh for Marketplace.