Electricity prices in [California] have begun turning negative on the main power exchange, the US Energy Information Administration (EIA) has revealed. Solar made up a record figure of nearly 40 per cent of the electricity sent to the grid in the California Independent System Operator's (CAISO's) territory for a few hours on 11 March, after utility-scale solar farms grew by almost 50 per cent in 2016, the EIA said. Solar capacity in the state has grown rapidly in the last few years. There was less than one gigawatt in 2007, but nearly 14GW by the end of last year. At this time of year, the large amounts of sunlight and the relatively low demand can produce too much electricity around the middle of the day. "Electricity demand in California tends to peak during the summer months," the EIA said. "However, in late winter and early spring, demand is at its annual minimum, but solar output, while not at its highest, is increasing as the days grow longer and the sun gets higher in the sky. "Consequently, power prices ... were substantially lower in March compared with other times of the year or even March of last year. System average hourly prices were frequently at or below $0 per megawatthour. In contrast, average hourly prices in March 2013-15 during this time of day ranged from $14/MWh to $45/MWh."