ᐅ Ground Source Heat Pump for a 200 m² Single-Family Home with Underfloor Heating, KfW55 Standard – Settings and Optimization

grericht schrieb:

So, we have two meters and two tariffs. But we don't have a photovoltaic system yet, and I decided to try it out first. I didn't know beforehand how much heating energy we actually consume.
As expected, it looks very tight whether this is worthwhile—and that’s even without photovoltaics.
With photovoltaics, I would strongly advise against it because you inevitably reduce self-consumption, and that is the "most valuable self-generated electricity." At least, I don’t know of any way to connect the same photovoltaic system to two power circuits for self-consumption. You would probably have to decide on which circuit you want to use the generated electricity. You could assign it to the heat pump’s consumption (which doesn’t make sense because the photovoltaic output is high in summer, while the heat pump’s demand is high in winter) or to the house electricity (which means that in summer—and possibly even in winter—your house electricity is fully supplied by photovoltaics, but the heat pump runs 100% on your heat pump electricity tariff). To me, that risk is too high because you’d lose some nice winter sunshine hours to support the heat pump’s self-consumption there. However, this also depends on the type of photovoltaic system you have. If it only produces from spring to autumn, you could run the heat pump separately—but we have a south-facing roof at 50° pitch, so I expect some output even in winter.
As a last option, you could also “split” your photovoltaic system, meaning one inverter for the part of the system dedicated to the heat pump’s self-consumption and another for the house electricity. I’m not sure if there are flexible options to allocate production (e.g., mostly to the heat pump in winter, and about 20% to the heat pump and the rest to house electricity in summer). But the energy supplier would have to cooperate and install two bi-directional meters. I believe they usually reject this (at least for the heat pump electricity meter, they probably won’t allow it).
And as I said, even for us, a second meter probably isn’t worthwhile (I can only tell for sure in five months). For us, the (low) base fees of the second meter almost cancel out the cheaper kilowatt-hour price. But that also depends on how much heating output you produce annually and with what seasonal performance factor.
If you also factor in that the heat pump loses efficiency and comfort, sometimes running into an energy supply lockout, I think that as of July 1st, we’ll have only one meter. Then we can calmly approach the photovoltaic topic.

Thank you for your detailed post. It helped me a lot.
I roughly calculated it. A second meter will cost us between 800 and 1000€ (around 870 to 1087 USD). The monthly difference between one and two tariffs is about 15 to 20€ (roughly 16 to 22 USD) at best. But here the heat pump tariff can continually rise, reducing the price advantage over the years. Since we plan to install a photovoltaic system within the next two to three years anyway, we tend to choose the solution with one electricity meter.
Our electrician mentioned that we might need the space for a second meter someday (you never know what the future holds), so he would install a second meter. However, we will decline this option. Thanks.

driver55 schrieb:

Where?
In the "orange" area, 2-3 K is recommended for the brine circuit and 6-7 K for the heating circuit.

What is the "orange" area?
Maybe I really misread it. I was quite surprised.
So far, at the end of the heating season, I have exactly 3 K difference:
brine outlet 8 (at the start of the heating period 9)
brine inlet 5 (at the start of the heating period rather 6)
Is that a good value? How much does the brine typically cool down by the end of the heating season? And what is a good starting value?

For the heating circuit, I only have a temperature difference of 5 degrees between the supply and return. What would that mean?

Pumpernickel1 schrieb:

Thanks for your detailed post. It helped me a lot.
I roughly calculated the costs. A second meter will cost us between 800-1000€ (around $870-$1080). The monthly difference between single and dual tariff rates is about 15€-20€ (around $16-$22) at best. But even here, the heat pump tariff could continually increase, reducing the price advantage over time. Since we plan to install a photovoltaic system within the next 2-3 years anyway, we are leaning towards the solution with just one electricity meter.
Our electrician said that the space for a second meter might be useful in the future (you never know what’s coming), so he would install a second meter. But we will pass on this option. Thank you.

I think that’s a good decision. Still, just to ask again: why does the second meter cost you 800-1000€ (around $870-$1080)? For our new build, it didn’t cost a single cent. It just took up some space in the distribution board. We rent the meter from the energy supplier, and the electrician wouldn’t care whether he connects the compressor to one meter or a second one, right? Or did I miss something and unknowingly spend a lot on the test? The electrician said (though this may not be correct) that the costs wouldn’t differ.

grericht schrieb:

I think that’s a good decision. Still, just to double-check: why does the second meter cost you 800-1000 EUR? In our new build, I believe it didn’t cost anything at all, just took up some space in the distribution board. We rent the meter from the energy supplier, and for the electrician, it shouldn’t matter whether the compressor is connected to one meter or a second one, right? Or did I miss something and actually invest a lot in the test? The electrician said (but that might not be accurate) that the costs wouldn’t really differ.

So, our electrician will be charging us this amount. He needs to install a larger meter cabinet with an additional meter for this. I haven’t received the exact quote yet, but it should be within that range.

Pumpernickel1 schrieb:

So our electrician will charge us this amount. He needs to install a larger distribution board with an additional meter. I will get the exact figure later, but it should be in this range.

Our electrician convinced us to get the largest distribution board anyway. There was plenty of room for the second meter there. Now I just hope he didn’t charge extra for connecting the compressor to a different meter.

Pumpernickel1 schrieb:

So our electrician will charge us this amount. He needs to install a larger electrical meter cabinet with an additional meter. I will receive the exact figure later, but it will be in that range.

That is really the worst-case scenario if the cabinet needs to be replaced.

The modification cost us about €150 (around $165) for the electrician. The meters themselves, their installation, the timer switch for blackout periods, etc., are free of charge, provided by the metering point operator and covered by the basic fees.
I can only advise everyone to check whether significantly cheaper electricity tariffs for heat pumps are available. If the difference is marginal, however, I would recommend not switching—saving 10€ (around $11) per year isn’t worth the effort.