The alternative heat point is interesting, you don't need to be able to heat your entire house with alternative heat for extended periods of time. If properly d

The alternative heat point is interesting, you don't need to be able to heat your entire house with alternative heat for extended periods of time. If properly designed, 99% of the hours of the year should be warm enough for the heat pump to provide 100% to heat and the remaining hours can be made up with a small space heater or a fire or something else minimal.