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On May 1, Germany ran almost entirely on renewables energy during the day
(transparency.entsoe.eu)
Some fossil-fuel-burning power plants were kept on at minimum operating levels (they're likely not designed for daily restarts) but provided less power than was used to pump water uphill in hydoelectric storage facilities.
Not impressed. Spain managed to run on almost nothing a few days ago.
Nobody ran anything that day. It was a mega-siesta.