ᐅ Heat pump/ventilation system with excessive energy consumption
Created on: 24 Jun 2025 07:44
G
Gintonik
Hello forum,
My brother-in-law sent me a screenshot from his photovoltaic app. The values shown there seem illogical and much too high to me. As far as I can interpret, his photovoltaic system generated 38 kWh and additionally drew 12 kWh from the grid. That adds up to 50 kWh for the day. He has a KfW40 house built in 2022, with a Tecalor THZ 504 heat pump/ventilation system. He also uses this system to cool his house.
The total seems far too high to me, but I have no personal experience with a heat pump/ventilation system. I have now asked him to document the electricity consumption on the meter every evening to see if he really consumes what the app shows. I once had my energy flow meter for my photovoltaic system connected incorrectly, so it showed my generated energy as consumption.
In recent days, we had warm/hot weather. During the day, when the cooling runs, the photovoltaic system supplies electricity. In the evening, when the sun is gone, there is no more power from the photovoltaic system, but then cooling should no longer be necessary.
Do you have any experience with such systems?
My brother-in-law sent me a screenshot from his photovoltaic app. The values shown there seem illogical and much too high to me. As far as I can interpret, his photovoltaic system generated 38 kWh and additionally drew 12 kWh from the grid. That adds up to 50 kWh for the day. He has a KfW40 house built in 2022, with a Tecalor THZ 504 heat pump/ventilation system. He also uses this system to cool his house.
The total seems far too high to me, but I have no personal experience with a heat pump/ventilation system. I have now asked him to document the electricity consumption on the meter every evening to see if he really consumes what the app shows. I once had my energy flow meter for my photovoltaic system connected incorrectly, so it showed my generated energy as consumption.
In recent days, we had warm/hot weather. During the day, when the cooling runs, the photovoltaic system supplies electricity. In the evening, when the sun is gone, there is no more power from the photovoltaic system, but then cooling should no longer be necessary.
Do you have any experience with such systems?
N
nordanney24 Jun 2025 08:20I would (or actually would have done it a long time ago) just turn off the Tecalor for half an hour. You can watch in real time what happens.
nordanney schrieb:
I would (or rather, I would have done it a long time ago) simply turn off the Tecalor for half an hour. You can then watch in real time what happens. Good idea, but I’ll have to do that myself since my brother-in-law isn’t exactly very tech-savvy.
Something else I noticed after looking at my image again:
I’m not familiar with the Senec app, so I’m just guessing, but isn’t it the case that something runs continuously at around 5 kW from about 8 a.m. to 9 p.m.? The orange area looks to me like the photovoltaic generation. If that’s correct, it should happen every day from roughly 8 a.m. to 9 p.m. Then it must be something that’s time-controlled.
You can also exclude individual sections in the app by tapping at the top. And yes, the orange line represents the consumption. You could have that displayed in even more detail. It works in the app down to the exact hour. Do as Nordanney suggested and turn off the heat pump for about 1 hour. Then monitor the consumption display in the app. The app updates every 5 minutes.
I suspect your brother-in-law fell for advertising promises,
about 5-7 heat pumps on the roof, 6 kWh (6 kWh) battery storage.
They calculate electricity consumption for the heat pump, cooling, household use, and so on.
The system was already too small on June 21st.
100% self-sufficiency is usually expected from March to October.
The battery can’t even cover the night consumption of 8 kWh (8 kWh).
I don’t see a washing machine, stove, or breakfast peak accounted for at all.
about 5-7 heat pumps on the roof, 6 kWh (6 kWh) battery storage.
They calculate electricity consumption for the heat pump, cooling, household use, and so on.
The system was already too small on June 21st.
100% self-sufficiency is usually expected from March to October.
The battery can’t even cover the night consumption of 8 kWh (8 kWh).
I don’t see a washing machine, stove, or breakfast peak accounted for at all.
Nida35a schrieb:
I suspect your brother-in-law fell for advertising promises,
about a 5–7 kW heat pump on the roof, 6 kWh storage.
They mention the heat pump’s electricity consumption, cooling, household usage, and so on.
The system is already too small as of June 21st,
100% self-sufficiency is basically possible only from March to October.
The storage can’t even cover the night consumption of 8 kWh,
I don’t even see a washing machine, oven, or breakfast peak demand considered. I have an 8 kWp system on the roof and a 10 kW storage unit in the basement myself. From April to September, I am always self-sufficient and do not buy any additional kWh. However, I don’t operate a heat pump, only a small air conditioner at most as needed. I agree that the system components are not well matched to each other. Still, that doesn’t explain a consumption of 5 kW/h over several hours. I will take a closer look at this issue myself over the weekend. Actually, I should be able to measure the current drawn by the heat pump using a clamp meter.
Malle Zwabber24 Jun 2025 13:33I interpret the chart a bit differently, but maybe I’m missing something. You don’t have a constant consumption of 5 kWh between 8:00 AM and 9:00 PM. During this period, you are almost 100% self-sufficient (green line). Around 2:00 PM, you have a power peak of about 4.5 kW (orange line). Overall, I think the consumption is quite high.
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