Congress will resume hearings today into last month’s massive blackout that darkened homes form Ohio to New York. The chairman of the federal energy regulatory commission along with several existing transmission monitoring groups want a system of mandatory reliability rules, the rules would be enforced by the groups. They say such a system would improve reliability because they have a broader perspective on electrical operations. Not everyone thinks this is a great idea. Opponents say the groups won’t add transmission capacity and will cost millions of dollars. The nation’s worst blackout affected 50 million people and shut down more than 100 power plants. Investigators have focused on failures of a power plant and lines owned by first-energy of Ohio. They say the blackout started in Ohio and Michigan before spreading.