These people have been (most likely) switching to heat pumps, not space-heaters. The heat you get from a light bulb is purely waste from the resistance of the

These people have been (most likely) switching to heat pumps, not space-heaters. The heat you get from a light bulb is purely waste from the resistance of the light bulb, so the output per unit of input will be around 1:1, comparable to that of a space-heater. Heat pumps are much more efficient, because they give you both the waste heat (from resistance) and heat from outside.