Hi,
The electricity meter for the subsidy can be a normal DIN rail meter. This and a heat meter should definitely be installed regardless of the subsidy. Otherwise, how else would one know how efficient the heat pump is? I wouldn’t rely on the heat pump’s values depending on the model. For many devices, this is simply calculated at runtime and has little to do with the actual values in reality.
The electricity meter for the heat pump tariff comes from the basic responsible metering point operator (usually the VNB) or from the contracted metering point operator. To use the photovoltaic electricity for the heat pump, a so-called cascade measurement must be done. Not all metering point operators do this. Additionally, the second meter causes extra costs that are not offset by lower electricity costs, as in new buildings only a little electricity is needed for the heat pump due to the usually low heating demand.
Your photovoltaic system will cover about 20%-30% of the heating demand. Much more for hot water. The remaining approx. 60%-70% of the electricity then has to be purchased. It is doubtful that enough electricity accumulates to make cascade measurement profitable. A second meter without cascade measurement is certainly more expensive than using one’s own photovoltaic electricity.
Regards Nika