[tgma]

Electricity is much more expensive than gas per J. You have to be ~3x more efficient to just break even.

[occz]

As it turns out, you regularly get a COP of >3 from heat pumps, as they don't need to generate the heat, they steal it from somewhere else (outside)

[tgma]

Right and you simply break even there so there's not much upside in terms of variable costs unless your electricity is somehow cheaper and not mainstream California prices.