Five board members of the Electric Reliability Council of Texas (ERCOT), Texas’s power grid operator, resigned Tuesday after the state power system failed during a deadly winter storm, leaving more than 4 million customers losing electricity amid subfreezing temperatures. All of the five board directors live outside Texas. Their resignations are effective Wednesday, just a day before Texas lawmakers are expected to question grid managers and energy officials about the failures during hearings at the state Capitol. ERCOT Chair Sally Talberg, Vice Chair Peter Cramton, and board members Terry Bulger and Raymond Hepper, wrote in a joint letter addressed to other ERCOT board members: “We want to acknowledge the pain and suffering of Texans during this past week. Our hearts go out to all Texans who have had to go without electricity, heat, and water during frigid temperatures and continue to face the tragic consequences of this emergency.” The letter was attached …