Many people worry data centers will increase their power bills, which are already going up. Ashley Fisher, of Helena, said a study by the University of Michigan shows examples of the way data centers drive up costs and places where “prices have doubled.” NorthWestern Energy has said data centers “must pay their fair share of the transmission, generation and distribution upgrades they require.” The filing from Earthjustice said NorthWestern Energy is under negotiations to at least double and potentially increase by tenfold its daily retail load to serve data centers. NorthWestern Energy could not be reached for additional comment in time for this story.