Chapter 21 of draft 2.9.3 from 02008 https://web.archive.org/web/20080906132444/http://www.infere... begins:
> In the last chapter, we learned that electrification could shrink transport’s energy consumption to one fifth of its current levels; and that public transport and cycling can be about 40 times more energy-efficient than car-driving. How about heating? What sort of energy-savings can technology or lifestyle-change offer?
and it goes on to talk about heat pumps, as today. So I think that even versions from 02008 got this right, though evidently that was at least the 13th numbered draft.