CLEVELAND, Tenn. (AP) -- An unusual commitment by Tennessee to cover the cost of any future carbon tax for green companies that make major investments here is being credited for luring two big solar energy developments worth more than $2 billion.

The tax break, which passed in the Legislature last year with little fanfare, promises that the state will offset increased costs from any future tax on carbon emissions for a select group of companies.

The credit would apply to any green energy supply chain company spending at least $250 million in the state. That includes the $1 billion Wacker Chemie AG plant announced in Bradley County this week, and the $1.2 billion Hemlock Semiconductor Corp. plant to be built in Montgomery County.

Both plants will make polysilicon, a material used to make solar cells.

(Copyright 2009 by The Associated Press. All Rights