By producing more energy, having less cars, better insulated houses, ... It's been calculated and described a thousand times by now by various institutes how this can be done. But obviously this can't be done in a few months, after the previous governments ignored experts for years.

> An electric heater usually consumes 2000 Watt, that is not really something that should bring the electric grid to its knees.

That's an additional 40GW when all gas-heated apartments use one of those heaters. You'd need ~30 additional nuclear reactors to sustain such a load -- the 3 remaining ones in Germany provide 1.4GW each.