Geothermal heat pump single-family house 200m² underfloor heating kfw55 - setting/optimization

Hello, I don't know if this is appropriate in this thread, but I will try anyway. We are building a single-family house with a geothermal heat pump and underfloor heating and plan to install a photovoltaic system in the next few years. Now the question arises whether a second electricity meter is necessary. It would certainly make sense for the heat pump tariff. However, our electrician said that if the photovoltaic system is installed, there will only be one electricity meter. One would have to calculate whether a second electricity meter makes sense or not. Unfortunately, I am completely confused here. How did you solve it? Second electricity meter yes or no and why? Thanks in advance.

doesn’t really fit here. We only have one meter for everything. Whether a second meter is worthwhile for you depends on your consumption and the tariffs offered to you. Just calculate it.

We are building a single-family house with a geothermal heat pump and underfloor heating and plan to install a photovoltaic system in the next few years. Now the question arises whether a second electricity meter is necessary. For the heat pump tariff, it would definitely make sense. However, our electrician said that if the photovoltaic system is installed, there will only be one electricity meter. One would have to calculate whether a second electricity meter makes sense or not. Unfortunately, I am completely at a loss here. How did you solve it? Second electricity meter yes or no and why? Thanks in advance.

Please use the search function. There are a multitude of threads on this topic.

We have only one electricity meter. Additionally, we have installed an intermediate meter to account for self-consumption and to be able to use the photovoltaic system 100%.

Hello, I don't know if this is appropriate for this thread, but I'll try anyway. We are building a single-family house with a geothermal heat pump and underfloor heating and plan to install a photovoltaic system in the coming years. Now the question arises whether a second electricity meter is necessary. It would make sense for the heat pump tariff. But our electrician said that if the photovoltaic system is installed, there will only be one electricity meter. You would have to calculate whether a second electricity meter makes sense or not. Unfortunately, I'm completely at a loss here. How did you solve it? Second electricity meter yes or no and why? Thanks in advance.

so we have 2 meters and 2 tariffs. but we don't have a photovoltaic system yet and I decided to just test it. I didn't know before how much heating energy we would consume. as expected, it seems very tight whether it pays off – and that's already without photovoltaics. with photovoltaics, I would strongly advise against it because then you inevitably reduce self-consumption, and that is the "most valuable self-produced electricity." at least I am not aware of any way to feed the same photovoltaic system into 2 electricity lines for self-consumption. you would have to decide in which line you want to consume the generated electricity. you can connect it to the heat pump consumption (which is nonsense because photovoltaics produce a lot in summer, but the heat pump needs a lot in winter) or to the house electricity (which means that in summer and possibly even in winter, your house electricity is completely covered by photovoltaics, but the heat pump is 100% powered from your heat pump electricity. I find the risk too high there that you lose a few nice winter sun hours to also support the self-consumption of the heat pump – but that also depends on what kind of photovoltaic system you have. if it only produces yield from spring to autumn, you can also run the heat pump separately – but we have a 50° south-facing roof. so I hope for some yield in winter). as a last option, you could certainly "split" your photovoltaic system. so one inverter with part of the system for self-consumption of the heat pump and the other for house electricity. no idea if there are options to make the distribution more flexible (so almost everything to the heat pump in winter and in summer about 20% heat pump, rest house electricity). but the energy supplier has to cooperate too, so that they install 2 bidirectional meters. I believe they exclude that anyway (at least for heat pump electricity they probably won't agree?!). and as I said, even for us, the second meter is hardly worthwhile (I can only say exactly in 5 months. for us, the (low) basic fees of the second meter almost consume the cheaper kWh consumption anyway. but that also depends again on how much heating capacity you produce in the year with which seasonal performance factor. but if you also consider that the heat pump loses efficiency and comfort, that it always gets locked out from the utility grid, then I believe that from 1.7. we will only have one meter. and then calmly approach the topic of photovoltaics.

here’s an update on my heating:
I tried different things. I basically turned off the room thermostats and control valves. I am still working with thermal balancing. I called the office that retroactively performed the heating load calculation for us. So either they did something unusual or I had often heard it differently before: the heating load of the rooms is the calculation of how much heating energy goes into them. But when they calculated the hydraulic balancing, they did not calculate how much heating energy comes into the rooms at which flow rate. They only calculated how much flow is needed in the individual circuits so that approximately the same heating energy can be input into each room at the same time.
Practically:
the heating load in the basement is much lower because only 15 degrees are to be reached there. But even there, based on pipe spacing and pipe length, they calculated that heating load x can be input in time y, just like in the bathroom and the other rooms. This means that the hydraulic balancing would only cause the basement to be closed much more often than the bathroom. But that helps me zero if I don’t have ERRs. That’s why I prefer simple thermal balancing and am quite satisfied with it. In the living area, due to the kitchen, many people, and sun, there are quite some temperature differences. I’m thinking about turning the ERR on there and then closing the control valve at a certain temperature.
question: currently I have control valves that are closed without power. That wouldn’t make sense here. Should I just replace them with ones that are open without power? Are there recommendations for ones that consume little power? I have 2W ones installed but heard there are also ones with 1W? There are immediately 5 circuits/valves connected to that room.

Regarding consumption: the COP has slightly dropped to about 4.75. However, the annual performance factor has been at 4.35 since May and I hope to end up with at least 4.4, possibly even 4.5. The source inlet temperature is now below 5 degrees. Let’s see where that goes.

question: I only have a temperature difference of about 3 degrees between the heat source inlet and outlet. I read that it can actually be 7 degrees. But I already reduced the pump to stage 2 out of 3. That didn’t improve much. At stage 1 it seems it no longer has enough power to pump. I immediately set it back to 2 because the inlet temperature dropped rapidly and I was afraid it might freeze. Is that normal?