California's renewable energy glut has a silver lining

NEW YORK: California wants half its electricity needs to come from renewables by 2025. Yet last month it reduced solar and wind production by the most on record. That's because the Golden State is building so much solar power that there's increasingly more available than can be used - and storage remains expensive. It's a similar story from Beijing to Berlin. It's not a bad problem to have, though. The cost of producing solar power has dropped by more than 80% over the past decade, according to the Department of Energy. That's thanks to both technological improvements and increased economies of scale. It's likely to continue. In many areas of the country wind and solar are already among the cheapest sources of energy; they account for around a fifth of California's electricity needs. Grid demand must match supply, though - or risk damaging equipment or even causing blackouts. So when there's a surfeit of power, prices go negative and force supplies to be taken offline. Last month, California curtailed about 225,000 megawatt hours of electricity from wind and solar. That's a record, equivalent to about 1% of the state's electricity demand and some 25 times as much as was switched off a year earlier.