Caution with cascade connection, only a few grid operators can really handle it and the electricity provider switch also becomes tricky. Yes, the heat pump cascade saves me a lot of money with heat pump & photovoltaic, but the stress is a plague. With my grid operator, it took >30 phone calls, 15 emails, and many pulled-out hairs until the billing department actually accepted what their own technical department reported to them. Most electricity grid operators (who then report the consumption to the electricity provider) know 99% of the time only "one meter is heat pump one meter is general electricity," and whenever I have to clarify something with them again, I always say first, "please connect me directly to the specialist department, it is about a heat pump cascade."