On another 100-degree day in Texas, Sean Whitaker lingered outside a Dallas cafe after polishing off an iced coffee, having switched off the power to everything back home except his refrigerator. As an unrelenting heat wave grips Texas for a second week, public appeals to stay hydrated and limit outdoor activities have come with another ask of the state's nearly 30 million residents: Conserve electricity if possible as demand on the power grid is stretched to projected record peaks. An early summer arrival of blistering temperatures — which have been blamed for at least two death...