ᐅ Photovoltaic system, heat pump, household electricity, and three bi-directional meters

Hello everyone,

We have bought a house with the following setup:

Photovoltaic system -> inverter -> meter ZE (photovoltaic generation) -> household electricity -> meter Z2 (household electricity) -> heat pump -> meter Z1 heat pump

ZE = meter with feed-in and non-return valve
Z1 = meter for consumption and feed-in
Z2 = submeter for consumption

All meters are bidirectional meters.

Now I don’t understand the following:
Why are three bidirectional meters needed here, or what is the purpose of this setup?
Unfortunately, I cannot find any information about this in the documents.

I am familiar with cascade connection involving 2 meters. I assume the generation meter is not an official meter, but rather installed purely to satisfy the owner's curiosity about how much electricity has been produced.

They are all meters from the local network operator (and are officially "sealed").
I might have to call the municipal utilities next week to see if they can clarify the situation.

It reads like measuring concept 8 with a third meter (ZE), so you don’t have to calculate yourself.

Sounds reasonable. But why is the third meter sealed (and charged for)? Wouldn’t a privately installed meter be enough?

Would be, but isn’t. In principle, you could also simply calculate what it shows yourself.