Heat pump on home electricity or separate? How to calculate?

But to be fair, you are not allowed to use this electricity for your heat pump - if you do, the extra meter for the heat pump is already worthwhile. Otherwise not...

That is generalized. We currently have a provider that allows it! These prohibitions date back to the time of night storage heaters, which really consumed electricity. Unfortunately, they are still found in various contracts today (but frankly, I wouldn’t care about that either ). When we cook for five, the electricity consumption is significantly higher than when the heat pump runs...

That's then a big exception - the vast majority have it in there. And nice that you don't care (me neither), it just doesn't help that you violate the terms and conditions with it, making such a comparison pointless.

I also know where it comes from - but if it's written there, it's written there...

Especially since a change then becomes difficult every year. You're still lucky now, next time it will look different...

(to be honest, I wouldn’t care either ).

For example, from a set of terms and conditions:
The supply of withdrawal points with backup power systems (for example, in the operation of combined heat and power plants), emergency generators, electric storage heaters, heat pumps, cash and/or chip card meters is excluded.

Why they exclude that doesn’t matter. They are allowed to. If you do it anyway, the law is not on your side.

Why it is excluded by them does not matter. They are allowed to. If you do it anyway, the law is not on your side.

That is probably right. But I also wrote, "that it would be all the same to me." Emphasis on "would," since I currently have a contract in which it is allowed! However, if I were ever faced with the decision whether to disregard the terms and conditions or not, I would of course have to think hard...

Are there higher fees for this portion of electricity or is it related to different electricity prices in summer/winter? Or why do they exclude the heat pump?

At midday, electricity in DE is practically free on the power exchanges - or at least cheaper than usual. Unfortunately, the heat pump often runs at night. Furthermore, they probably also pay peak fees for load (but I don't know), and they definitely put in 10 kW (large older heat pumps).