U.S. grid operators on Saturday stepped up precautions to avoid rotating outages as frigid weather strained power systems, pushing spot wholesale prices on the PJM Interconnection above $3,000 per megawatt hour, a standard unit for electricity. PJM, which serves 67 million people in 13 states and Washington, D.C., raised its forecast for Tuesday to 147.2 gigawatts, an all-time winter high. Dominion Energy, whose Virginia territory hosts a major concentration of data centers, said ice could become one of the largest winter events to hit its operations. The cold snap lands as utilities and regulators try to adjust to around-the-clock demand from AI data centers, a type of load that does not fall much at night or in winter. Philip Krein, a power-grid expert at the University of Illinois Urbana-Champaign, said the narrowing gap between winter and summer peaks is squeezing maintenance windows for power plants. “The maintenance season is being squeezed like never before,” Krein said.