“More than half of the renewable energy flowing across the grid at that moment on Saturday came from large solar facilities and wind farms. The [California Independent System Operator’s] numbers do not even account for electricity from rooftop solar arrays,” a news report observes. “Overall, renewables accounted for 42 percent of the California grid’s power on Saturday, not counting the large hydropower plants.”

Such successes are key to ensuring that renewable energy sources become more and more mainstream as we continue to wean ourselves off fossil fuels so as to mitigate the worst effects of climate change fuelled by our relentless emissions of greenhouse gases. In California itself, which is one of the most progressive states in the United States, by law utilities will have to obtain a third (33%) of their electricity from renewable sources by 2020 and a full half of it by 2030.

This achievement is a welcome sign that this will indeed be doable. “The fact that the grid can handle 67 percent renewable power from multiple sources — it’s a great moment, and it shows the potential we have,” observed Sachu Constantine, director of policy at the Center for Sustainable Energy, a nonprofit clean energy advisory firm in Berkeley.