That "absolute worst case" happens in my house most of the winter, and it's common throughout the rich world. The only place it isn't common is where people don't have electricity yet. Even in Brazil, where nobody needs a space heater, electric water heaters are common.

When that absolute worst case is happening in the house's living space, we can and do "convert" heat to electrical energy savings 1:1, because every joule "wasted" by cooking food with gas, or heating the house with a corn stove, or warming up the floor with sunlight for passive solar gain, is another joule earlier that the space heater's thermostat will turn it off.

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rcxdude an hour ago | parent [-]

Sure, you're using the themodynamically worst heating technology possible (I don't think I have ever lived in a house that used resistive electric heating). That still doesn't make it a useful comparison overall where people often pick better options, nor does it make it so that you're actually converting the other way when you use better options.

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kragen an hour ago | parent [-]

As I explained 5 comments up this thread, people are going to stop picking those "better" options because they're no longer economical. I think you just didn't notice that part of my argument, because you never responded to it.

Also, I don't think it's accurate to describe electrical resistance heating as "the thermodynamically worst heating technology possible". Electrical resistance heating is generally close to 100% efficient. It's actually thermodynamically possible to make heaters that are less than 100% efficient; MacKay explains, for example, that he heats his house with a 90%-efficient condensing boiler, and it's common for fireplaces to be around 20% efficient, because most of the heat goes up the chimney instead of heating your house.

Fireplaces are actually thermodynamically possible machines. I understand that you've never seen one, but I assure you that they do exist.

I've actually lived in houses where the fireplace had negative efficiency at times, sucking more heat out of the house (in the form of warm air) than they added back in the form of radiation.

	▲	rcxdude an hour ago \| parent [-]
		That only makes sense in a situation where renewables have already more than taken over, which kind of makes the point moot. I'll concede your point that traditional fireplaces are even worse than resistive heating, though not that a gas condensing boiler is because you're not getting 90% of the energy in the gas out as electricity.