If you’re trying to heat your home, every electronic device becomes 100% efficient. All its “waste” heat becomes wanted heat. That it might only be 40W of heat is not the point.
Every electronic device is 100% efficient after the electricity has already been generated and delivered, sure, but a bunch of efficiency losses occurred before that. If you’re comparing methane burned on-site in a furnace to methane burned at a power plant, transmitted to the site as electricity, and then used for electric resistance heating, burning on-site is gonna be better even if the furnace loses more heat up the chimney than the power plant does.
Not how heat works.
If you’re trying to heat your home, every electronic device becomes 100% efficient. All its “waste” heat becomes wanted heat. That it might only be 40W of heat is not the point.
Every electronic device is 100% efficient after the electricity has already been generated and delivered, sure, but a bunch of efficiency losses occurred before that. If you’re comparing methane burned on-site in a furnace to methane burned at a power plant, transmitted to the site as electricity, and then used for electric resistance heating, burning on-site is gonna be better even if the furnace loses more heat up the chimney than the power plant does.
Also, a heat pump is “300%-500% efficient” in the sense that it moves 3x-5x as much heat as it uses. See also: https://en.wikipedia.org/wiki/Coefficient_of_performance