California passed a milestone in March as part of its bid to power the whole state sustainably. On March 11, for the first time ever, more than half the power needs of the entire state came from solar power for a few hours, according to data from the U.S. Energy Information Administration. The power came from a combination of utility-scale solar PV farms, solar thermal plants and the panels installed on private homes. Based on the data it collects, the EIA estimated that in each hour of peak times, that total capacity produced 4 million kilowatt-hours of electricity on March 11. That’s a massive and rapid change: just 15 years ago, the state produced almost no power from solar at all. The spikes in solar output also have a significant effect on California’s wholesale energy prices, which dipped to zero or even to negative territory this spring during certain hours, the EIA said. That’s in sharp contrast to the same hours (8 a.m. to 2 p.m.) in the month of March between 2013 and 2015, when average hourly wholesale prices ranged from $14-45 megawatt-hour.