Zero. There are batteries that come in car shape and with wheels. People pay for them and there will be tens of millions, eventually 250m. They are mostly stationery (23+ hours/day) and are used 20 mins - 1 hour/day. They form a gigantic distributed storage reservoir, can absorb excess power (and get paid for it! energy prices go negative!) and supply power back to the grid when needed (and get paid again!).