You also need to compare: * natural gas -> home furnace -> fire -> warm air vs * natural gas -> fire -> heat -> electricity in massive generator -> home

You also need to compare: * natural gas -> home furnace -> fire -> warm air vs * natural gas -> fire -> heat -> electricity in massive generator -> home -> heat pump -> warm air The latter is, surprisingly, something like 2x the efficiency because while large scale electricity generation from gas is only about 40% efficient, you can get a COP in the neighborhood of 5x on the heat pump. The part that isn't obvious is that the fantastical-sounding "5x" isn't really about energy efficiency but rather about changing the problem from "generating heat" to "moving heat from one place to another".