Some of the extra consumption isn't actually going to impact the last-mile grid too badly. If we go down the path of "all electric motoring, and all electric home-heating via heatpumps" (you cant do district heating off a windmill.) then that demand can all be time-shifted trivially, so existing wiring out to residences would need only modest upgrades. But the production side? That is going to need beefing up. A lot.