They produce more energy than they use in the summer with solar panels, but consume more than they produce in the winter when heating (the higher insulation levels and GSHP *do* substantially reduce this use over a conventional home) with the plan of ‘netting out’ over the course of a year.

Why is this important? The eventual outcome of this will not be no energy bill, but likely a flat ‘availability’ charge close to your present electrical bill for taking the excess when you don’t need it and providing the extra when needed.

Not saying they aren’t good or worthwhile, but they are also not a panecea.