On older homes, with much worse insulation, this would immediately be a problem.
Heat pumps are great, but they absolutely need some kind of emergency heat back up.
No, that's just not functional. "Less efficient" means consuming more joules of electricity but still providing the required function.
> Heat pumps are great, but they absolutely need some kind of emergency heat back up.
They include it. You were sold an inadequate pump for your situation.