> So you have all the heat pumps going on full blast on the coldest days, all together. It's a huge spike in energy demand. As long as the grid can deliver it fine, but when it doesn't the potential is catastrophic.

Repalce heat pumps with gas furnaces and you have an equally true sentence, if "the grid" is the gas grid.

Gas usage also spikes on those cold days. You know what people do to prevent this being an issue? Storage. Nothing you couldn't also do with electric power.