[OJFord]

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.

[pmoleri]

Unfortunately by that metric other electrical heaters tend to 0% efficiency because they are not making use of the virtually unlimited energy outside the buildings.

The 400% metric let's you compare with other heaters, the 100% is kind of useless.

[OJFord]

They're not using them as an input, so.. obviously they're not included in the input/output calculation?