The partial solar eclipse on Friday, 20 March 2015 was a test case for a power system in which half of all power will eventually come from wind, sun and other energy sources. The solar eclipse was manageable in 2015 because network operators had equipped themselves ahead of time. They had contracted power production that could be quickly revved up and back down again. For the anticipated flexibility needs in 2030, the technological possibilities for this kind of balancing act already exist. But they must be continuously developed.