On the evening of Sept. 9, 2026, with a heat wave pushing electricity demand across California toward its limits, more than 140,000 home batteries started discharging at the same time. Over a three-hour window, they sent more than 580 megawatts of power into the state's grid, roughly what a large conventional power plant puts out. Nobody broke ground on anything and no fuel got burned. The batteries were already mounted on garage walls across the state, and software told them when to go. That's a virtual power plant, and it's quickly becoming one…