I know. It's only >100% 'efficient' if you ignore the input of 'outside heat'. That is not a normal calculation, and not really called 'efficiency'.
It's desirable for multiple reasons, of course, but it's not efficiency.
It's desirable for multiple reasons, of course, but it's not efficiency.
The 400% metric let's you compare with other heaters, the 100% is kind of useless.