BOISE — An Idaho wind developer that recently suspended projects faces a new challenge: a federal lawsuit filed by a Virginia-based energy giant for missing millions in payments for turbines it agreed to buy less than four months ago.

Exergy Development Group LLC of Boise failed to pay up to $37.9 million for 32 turbines that were to be transported to Idaho from Pennsylvania, according to the lawsuit filed by a unit of AES Corp. in U.S. District Court in Idaho.

Arlington, VA.-based AES said Exergy signed the contract on May 25 and made an initial, nonrefundable deposit of $1.7 million on May 30, but missed a second deposit of $8.7 million on June 5. Exergy renegotiated the turbine deal with AES after failing to make payments, but reneged on that deal, too, according to the lawsuit.

"Defendant has breached a contract with plaintiff to purchase 32 wind turbines and related equipment," lawyers for AES wrote in the filing last week.

Until just months ago, Exergy was outwardly riding high as Idaho's biggest energy developer .

In 2010, it completed the state's biggest wind project in southern Idaho after partnering with General Electric Co. on 183 megawatts made possible by federal and state tax incentives.

Internally, however, it's now clear that Exergy's business in Idaho has been unraveling.

James Carkulis, the company's president, said last month that unresolved rules governing alternative energy projects in Idaho had made investors wary, forcing Exergy to put $323 million of its 2012 developments on hold. Two weeks ago, Exergy announced it was giving up contract rights to 116 megawatts of wind plants in Twin Falls, Lincoln and Bingham counties.