It’s a straightforward thermodynamic equation - x fuel burnt (and useful heat from that) vs maximum theoretical efficiency for heat pumps for equivalent heat.

The reality is likely worse for a number of reasons, but even if way better it doesn’t get around that you’d need many multiples of the entire electrical grids peak capacity to come close. And that is assuming there is zero other load on the grid, which isn’t going to happen.

If everyone completely redid all their structures and all their use of heating, and installed all the best heat pumps, AND doubled grid capacity, maaaaybe. But we’re talking massive amounts of Capital. Capital that used to be cheap, but isn’t anymore.

Far more Capital than likely has been spent so far on renewables too, but it’s hard to calculate it because of the sheer distortion that it would cause trying to do something of this scale.

It might be legitimately cheaper to buy Northern Africa and move all Germans there instead (in new construction). That seems pretty unlikely for sócio-political reasons though.