The debate over whether the Environmental Protection Agency should use cost-benefit analysis to help determine possible upgrades to existing powerplants has hit the Supreme Court. Oral arguments on Dec. 2 dealt with an appeal of a lower-court decision striking down a 2004 EPA rule allowing costs of upgrades to be weighed against environmental benefits.

At issue are older powerplants that use once-through cooling systems, which draw millions of gallons of water to cool their facilities. Environmental groups want older plants to be retrofitted with closed-cycle cooling systems, which use cooling towers. Entergy Corp. argues that upgrade costs could approach $1.5 billion at its Indian Point nuclear plant in New York. A ruling is expected by July, when the court’s session ends.