Hello everyone,
We have an 8 kW air-to-water heat pump from Kermi and a KfW55 house with about 200m² (2,150 sq ft). Currently, the indoor temperature is quite warm at 24.5°C (76°F). Yes, I know that is quite high. The consumption figures are only for the underfloor heating and are separate from the hot water usage.
I understand that the higher temperature leads to increased consumption, but could it possibly be too high?
We live just north of Hanau and in December maintained around 23°C (73°F) with a daily consumption of 6-8 kWh. When it got colder around Christmas, consumption rose to about 20 kWh. It has gotten even colder recently (-6 to 2°C / 21 to 36°F), and we simultaneously raised the temperature to about 24°C (75°F), resulting in a consumption of 30 kWh now.
I read that average consumption is based on 19°C (66°F), and for every degree above that, you need roughly 10% more energy. That would put us at about 60% higher consumption, but is 30 kWh then reasonable? According to the KfW application, we require around 30 W/m² (3 W/sq ft), which totals about 6 kW. But what exactly does that 6 kW refer to — over 24 hours? At what outside temperature? With an indoor temperature of 19°C (66°F)?
We had days in December with consumption as low as 6 kWh, which I think is quite good. However, with a few degrees colder weather and the heating curve increased by 1°C (2°F), the consumption jumps so much? By the way, we heat only via the heating curve, without any additional controllers.
Thanks in advance 🙂
We have an 8 kW air-to-water heat pump from Kermi and a KfW55 house with about 200m² (2,150 sq ft). Currently, the indoor temperature is quite warm at 24.5°C (76°F). Yes, I know that is quite high. The consumption figures are only for the underfloor heating and are separate from the hot water usage.
I understand that the higher temperature leads to increased consumption, but could it possibly be too high?
We live just north of Hanau and in December maintained around 23°C (73°F) with a daily consumption of 6-8 kWh. When it got colder around Christmas, consumption rose to about 20 kWh. It has gotten even colder recently (-6 to 2°C / 21 to 36°F), and we simultaneously raised the temperature to about 24°C (75°F), resulting in a consumption of 30 kWh now.
I read that average consumption is based on 19°C (66°F), and for every degree above that, you need roughly 10% more energy. That would put us at about 60% higher consumption, but is 30 kWh then reasonable? According to the KfW application, we require around 30 W/m² (3 W/sq ft), which totals about 6 kW. But what exactly does that 6 kW refer to — over 24 hours? At what outside temperature? With an indoor temperature of 19°C (66°F)?
We had days in December with consumption as low as 6 kWh, which I think is quite good. However, with a few degrees colder weather and the heating curve increased by 1°C (2°F), the consumption jumps so much? By the way, we heat only via the heating curve, without any additional controllers.
Thanks in advance 🙂
For your information:
I lowered the heating curve by 1 degree 72 hours ago. After that, consumption dropped to 20 kWh per day (heating only; domestic hot water remained stable at 2–3 kWh). Operating hours decreased from about 17 hours to around 12 hours per day. If I add the fact that the system consumes about 200 watts more than indicated, this adds roughly 2 kWh to the 20 kWh. I suspect that the 20 kWh refers to the pure compressor power consumption, while the 200 watts are used for controls and other components.
During this period, the temperature rose on average by approximately 1.5°C (2.7°F).
In short:
- Target supply temperature lowered from about 30°C (86°F) to about 29°C (84°F)
- Outdoor temperature on average about 1.5°C (2.7°F) warmer
- Consumption for heating decreased from 30 kWh to 20 kWh
Thanks! At the start of this thread, I wasn’t sure if these values were good or bad. I’m relieved that they are good and very satisfied that they are actually excellent.
If anyone wants more statistics, just let me know.
I lowered the heating curve by 1 degree 72 hours ago. After that, consumption dropped to 20 kWh per day (heating only; domestic hot water remained stable at 2–3 kWh). Operating hours decreased from about 17 hours to around 12 hours per day. If I add the fact that the system consumes about 200 watts more than indicated, this adds roughly 2 kWh to the 20 kWh. I suspect that the 20 kWh refers to the pure compressor power consumption, while the 200 watts are used for controls and other components.
During this period, the temperature rose on average by approximately 1.5°C (2.7°F).
In short:
- Target supply temperature lowered from about 30°C (86°F) to about 29°C (84°F)
- Outdoor temperature on average about 1.5°C (2.7°F) warmer
- Consumption for heating decreased from 30 kWh to 20 kWh
Alessandro schrieb:
Those are excellent values! 🙂
Thanks! At the start of this thread, I wasn’t sure if these values were good or bad. I’m relieved that they are good and very satisfied that they are actually excellent.
If anyone wants more statistics, just let me know.
A
Alessandro20 Jan 2021 11:39Have you all disabled the hot water circulation? It actually consumes a lot of electricity.
D
Daniel-Sp20 Jan 2021 12:42If a circulation system is installed, it must run at least once a day; otherwise, there will be stagnant piping, which is a breeding ground for germs.
We had deactivated the circulation due to energy loss. I haven't had the chance to control the pump with a timer or similar device yet, as the line is directly connected to the electrical panel. So far, the assumption was that I only need to switch the pump on occasionally, not at least once daily. It has been off for about three weeks now.
M. Gerd schrieb:
We had the circulation turned off because of energy loss. I haven’t gotten around to controlling the pump with a timer or something similar yet, since the line is directly connected to the electrical panel. Until now, the assumption was that I only need to turn the pump on occasionally, and not at least once daily. It has actually been off for about 3 weeks. It even depends on who you ask; I’m not exactly sure what the regulation is called, whether it’s a DIN standard or something else, but it states that the circulation should not run more than 8 hours per day... though I’m sure someone here will know for sure.
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