I have one of those. It’s called “Termowentylator” in our house.
I used it in my office before we had the heat pump. I often work during the night in my office so didn’t want to waste energy heating the whole house.
Then I experimented with the heat pump. As you can see from last night, the heat pump uses 1.2kW to keep the whole house ticking along:
So now I’ve decided to use the heat pump during the night instead of termowentylator.
As we all know, mine is oversized for most of the time so I do get a lower CoP but I mitigate that by switching it on and off. I have the luxury that the Ecodan gets up to reasonable efficiency relatively quickly.
Just for the record, it did actually manage a long run yesterday and it was pretty underwhelming efficiency. We were warm though. The effective temp was just hovering below zero.
You might argue our heat loss is about 4.6kW@0 °C from that chart so having a 14kW heat pump is clearly much bigger than required.