SACRAMENTO, Calif. — In her Stockton apartment, Esther Johnson has been freezing pots of water overnight for relief from California’s historic heat. In the morning, she wraps them in towels, puts them at the foot of the couch and blasts them with fans to create some cool air. It was 107 degrees outside on Tuesday, the day several cities broke all-time heat records. Inside, it was 96 degrees. Californians blasted their air conditioning so much this week they nearly overwhelmed the state’s electricity grid. For many of the 24% of households across the state without A/C, each day has been a miser...