The wind power industry may have won the production tax credit war, but there’s still one more battle to fight.

The sector is eagerly waiting for federal tax experts to give detailed guidance that interprets a language change to the PTC, the crucial industry support that was extended by one year in the final fiscal cliff package.

The new language allows companies to take advantage of the PTC if they begin construction by the end of 2013, rather than when a project is placed into service, as previously required.

The tweak marked a major victory for the wind industry, which argued that the existing PTC language didn’t give companies enough time to claim the 2.2-cents-per-kilowatt-hour tax credit.

But the federal government still must decide this looming question: How do you define “begin construction”? That definition could have huge ramifications for wind developers.

“This is a big deal,” said David Burton, a partner at Akin Gump.

The wind industry is hoping the federal government takes a cue from the Treasury Department, which said in 2009 that companies qualified for the 1603 cash grant program once they invested 5 percent of the total cost of their project.

Under that scenario, developers would not need to complete the time-consuming legwork required before starting to build a wind farm in order to take advantage of the tax credit. Instead, developers would just need to meet the modest investment threshold.

If adopted, that guidance would ease the pressure on companies to rush to break ground on projects before the tax credit expires at the end of 2013.

The alternative is a more traditional definition of beginning construction that would require companies to start building a project before it qualified for the tax credit.

“That probably means guys in hard hats, backhoes and cranes,” Burton said.

“You have to do an awful lot of work in a pretty short amount of time if you use the dictionary definition of ‘start construction,’” Burton said, adding that companies would have to secure land, develop purchase agreements for wind turbines and obtain the necessary permits.

Burton said the industry is confident that the federal government will use the 5 percent model. Joint Committee on Taxation Chief of Staff Thomas Barthold has told the Senate Finance Committee that companies need to make a minimal expenditure to claim the tax credit, giving the industry hope that the government will incorporate it, Burton said.

It’s unclear exactly which government entity will issue the guidance on the PTC and when. It could be the Joint Committee on Taxation, the Internal Revenue Service or the Treasury Department, Burton said.

The IRS and the Joint Committee on Taxation did not immediately provide comment for this story.

The American Wind Energy Association, the wind industry’s trade group, said the expected PTC guidance “is routine practice in terms of implementing tax credits.”

“The PTC extension, as was originally passed by the Senate Finance Committee on Aug. 2 with bipartisan support, accommodates the business timelines of the industry. The American wind industry is now getting busy advancing projects to construction this year,” AWEA said in a statement.