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 🙂
There is a thread somewhere that is regularly updated about electricity consumption... it mainly focuses on the consumption of heat pumps. You should look it up.
P.S. Values tend to reflect the whole year... so high values in summer balance out over time 🙂
M. Gerd schrieb:Wow. Isn’t that value rather high? How long have you been living in the house? Is there a controlled mechanical ventilation system installed? So why is the humidity level still so “high”?
It is between 40-50%. Why?
M. Gerd schrieb:We also keep it around 23/24 degrees Celsius (73/75 °F), and I tend to feel cold easily. So I don’t find it unreasonable when someone reaches for a blanket and a hot water bottle... Living room and fleece blankets are there to make things a bit cozier. Unfortunately, we have a supply air vent that causes drafts right at my sofa spot... so what.
and rather than shivering and grabbing the blanket, I prefer to turn up the heating ;-)
P.S. Values tend to reflect the whole year... so high values in summer balance out over time 🙂
T_im_Norden schrieb:
Then take a look at how much heat you produced with 30 kW of electricity.155 kW were generated in the last 24 hours, covering both heating and domestic hot water. Heating used 32 kWh and hot water 3 kWh. The average COP has dropped slightly due to the cold days and is currently at 5.3. Heating alone is 4.9 and hot water 3.6.ypg schrieb:
Wow. Isn’t that value quite high? How long have you been living in the house? You have a controlled ventilation system, so why is the indoor humidity still so “high”?I checked again. Last night it was 40%, and now it’s 35% in the living room. But I remember that a few weeks ago it was sometimes as high as 50%.P.S. We lowered the temperature curve by 1°C (2°F) this morning because 24°C (75°F) is really quite warm, and as @ypg said, you can always use a hot water bottle and blanket for extra comfort.
Bookstar schrieb:
A COP of over 5 with an air-to-water heat pump at these temperatures? I didn’t realize something like that was already available on the market :O We also paid a good amount for it 🤨 We specifically chose the monoblock, but we are also somewhat positively surprised. Here are a few screenshots from the past weeks. December in particular looks quite good ;-)
In December, we had the circulation of the TWE running 24/7, which is why we consumed about 10 kWh per day here.
D
Daniel-Sp17 Jan 2021 11:58M. Gerd schrieb:
155 kWh were generated in the last 24 hours, consisting of heating and hot water. Heating was 32 kWh and domestic hot water 3 kWh. The average COP has dropped slightly due to the cold days and currently stands at 5.3. Heating alone is 4.9 and hot water 3.6.
How can the total COP be higher than the COP for hot water and heating separately?
Did you calculate them yourself using external heat meters and electricity meters, or does the heat pump provide these values directly?
The heat meters built into heat pumps are usually not very accurate and often show higher heat output than calibrated external heat meters (which is not surprising).
Daniel-Sp schrieb:
How can the overall COP be higher than the COP for hot water and heating separately???
Did you calculate it yourself using external heat meters and electricity meters, or does the heat pump provide these values itself?
The heat meters built into heat pumps are usually not very accurate and often show a higher heat output than calibrated external heat meters (no surprise there).Where exactly is the overall COP higher than the COP for heating and domestic hot water? I am just surprised that there are not always values available for domestic hot water.Currently, I am not using any external heat meters. I once considered using external meters, but just integrating calibrated meters into my KNX system would cost me several hundred euros. This way, I could measure consumption for photovoltaic, battery, heating, and household myself. I can do that already now, but not with calibrated meters supplied by the manufacturer. However, I don’t see the added value clearly yet. Yes, I would be interested in exact values. Is it worth several hundred euros to me?
What kind of deviations can we expect? 1-3%? 3-5%? 5-7%? 7-10%?
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