A state tax credit that helped propel Oklahoma to third in the nation in its capacity to generate electricity from wind is coming to an end, but it will be years before state coffers see results of the change. Gov. Mary Fallin on Monday signed legislation that rolls back a 10-year tax credit for electricity generated by zero-emission facilities that was launched in 2003.Under the measure, zero-emission facilities must be operating by July 1 this year to qualify for the credit, instead of Jan. 1, 2021. It is one of several revenue proposals that Oklahoma lawmakers are considering as they struggle to close an estimated $868 million budget shortfall. But closing the window of eligibility will have no short-term impact on state tax collections, according to fiscal analysts. The first tax year that the change will be fully in effect is 2027.