> Look, upthread comment implied pretty clearly that a particular heat pump as installed would "work" until zero net energy flow at "-20C" I did not read it th

> Look, upthread comment implied pretty clearly that a particular heat pump as installed would "work" until zero net energy flow at "-20C" I did not read it that way at all. To me they are clearly talking about the point at which your heat pump no longer provides a efficiency gain over a purely resistive heater. I think where you went wrong is reading "gain" as "heat gain" rather than "efficiency gain". While the usage of "gain" is sort of ambiguous there, the rest of the comment thread makes it clear that the term 1:1 is not discussing the point at which your heat pump stops producing any heat but the point at which it becomes inefficient. > that's not the threshold you use to size a heat pump as is doesn't reflect a steady state I don't think anyone except you was talking about sizing the system, but about selecting the system type given the climate. If you had come into this just saying "here's my relevant experience with sizing heat pumps", that would have been productive. However you strongly asserted that the OP was using the wrong metric, which they weren't. > I'm deeply sorry if this offended you for some reason, I'm not sure why you think I am offended.