There will always be fringe markets for products that use renewable energy to provide marginal heating comfort. These markets survive because early adopters willingly sacrifice superior comfort as the perceived price for using renewable energy.
However, I contend that renewable-energy heating systems will only gain mainstream acceptance if they provide comfort that’s as good — if not better — than conventional systems. The typical North American consumer will not knowingly sacrifice comfort just to shift the source of their heating energy from conventional to renewable energy sources.