[Retric]

Heat loss is linear.

Resistance heating is linear. Furnaces using slightly colder outside air are just a tiny bit less efficient, but it’s really close to linear. Heat pumps are non linear and do use electricity from natural gas.

[nawgz]

So if I understand you, the only non-linear effect in play is that Heat Pumps are MORE efficient when the temperature differential is higher, is that correct?

[Retric]

Heat pumps are LESS efficient when the temperature differential is higher.

https://learnmetrics.com/heat-pump-efficiency-vs-temperature...