ᐅ Should the photovoltaic system be taken into account when sizing the heat pump or not?
Created on: 28 Sep 2023 21:34
R
Radfahrer
Hello,
I am considering installing a photovoltaic system.
Currently, my household electricity consumption is about 3800 kWh per year.
Additionally, I have a heat pump with a consumption of around 2900 kWh per year.
Now, I am unsure whether it makes sense to size the photovoltaic system larger to cover the heat pump since heating is mostly needed during the darker months.
In summer, there is probably excess electricity available, which could be used for water heating.
It should also be taken into account that the heat pump usually runs at night in winter and consumes about 3.3 kW.
For water heating only in summer, I would have the option to choose the operating times freely.
However, the air-source pump then requires 5 kW.
Unfortunately, my roof areas are not optimal.
It is a one-story house with a hip roof at 18° (18°) pitch, and the large surface faces almost north.
Three surfaces facing south or west would be sufficient for nearly 10 kWp.
What would you advise me?
I am considering installing a photovoltaic system.
Currently, my household electricity consumption is about 3800 kWh per year.
Additionally, I have a heat pump with a consumption of around 2900 kWh per year.
Now, I am unsure whether it makes sense to size the photovoltaic system larger to cover the heat pump since heating is mostly needed during the darker months.
In summer, there is probably excess electricity available, which could be used for water heating.
It should also be taken into account that the heat pump usually runs at night in winter and consumes about 3.3 kW.
For water heating only in summer, I would have the option to choose the operating times freely.
However, the air-source pump then requires 5 kW.
Unfortunately, my roof areas are not optimal.
It is a one-story house with a hip roof at 18° (18°) pitch, and the large surface faces almost north.
Three surfaces facing south or west would be sufficient for nearly 10 kWp.
What would you advise me?
N
nordanney18 Mar 2024 11:31tristan01 schrieb:
For more than two roof surfaces, you also need two inverters, and that makes it expensive.It depends on the size of the system. Your statement is not generally correct.tristan01 schrieb:
The fact is that a battery storage increases your self-sufficiency compared to a system without storage. The battery basically serves to cover the household energy demand at night. It can also support the heat pump in winter. The heat pump operates with an electric heating element in winter.However, the battery is hardly charged in winter. Or rather, the heat pump (which, by the way, always runs electrically, not only with the heating element – which, by the way, is not needed if the system is properly designed) consumes so much electricity in winter that a battery storage won’t get you very far (my 10 kW system only produced about 120 kWh last December; that’s not much to work with).
nordanney schrieb:
However, the storage system hardly charges during winter. Or rather, the heat pump (which, by the way, always runs electrically, not just with the heating element – which, if properly sized, is not needed) consumes so much electricity in winter that having a storage system doesn’t get you very far (my 10 kW system only produced about 120 kWh last December, which isn’t much to work with).You are probably right. Since we haven’t even moved in yet, I unfortunately don’t have long-term data. Regarding production, I notice that my system generates electricity even with little sun. It’s limited, but at least it produces something.
W
WilderSueden18 Mar 2024 12:11It always produces something when it’s light. But on a dull winter day, our 6.5 kWp system often only produces around 50 W, and not even for 8 hours. The profitability mainly comes during the transitional seasons, when the heating is still running but the days are already longer and brighter.
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nordanney18 Mar 2024 12:16WilderSueden schrieb:
The cost-effectiveness becomes especially noticeable during the transitional periods, when the heating is still running but the days are already longer and sunnier.Or in summer, when you can fully power the air conditioning, pool pump, electric car, or similar devices.Depending on the weather, we currently use about 15-25 kWh per day for household electricity and heating power with our 9 kW heat pump. Two adults, two small children in a renovated older building. The washing machine and dryer run almost daily, and the dishwasher is sometimes used twice a day due to working from home.
Right now (and again in autumn) is exactly the time when a battery storage system would be worthwhile because at night, for example, during freezing temperatures, we consume around 10 kWh of heating electricity, and sunny days are followed by cold nights. With our 12 kWp solar system facing south, we feed in 40-50 kWh on such days.
In really overcast weather, the photovoltaic system still covers our base load (~250-300 W), which is quite nice.
We don’t have a storage system and probably won’t buy one for the time being unless there are good offers (the solar installer priced a 10 kWh battery at 7000 euros). In summer, we never empty it at night, and in winter it usually doesn’t fill up during the day.
Right now (and again in autumn) is exactly the time when a battery storage system would be worthwhile because at night, for example, during freezing temperatures, we consume around 10 kWh of heating electricity, and sunny days are followed by cold nights. With our 12 kWp solar system facing south, we feed in 40-50 kWh on such days.
In really overcast weather, the photovoltaic system still covers our base load (~250-300 W), which is quite nice.
We don’t have a storage system and probably won’t buy one for the time being unless there are good offers (the solar installer priced a 10 kWh battery at 7000 euros). In summer, we never empty it at night, and in winter it usually doesn’t fill up during the day.
leschaf schrieb:
For example, with subzero temperatures, you can easily burn through around 10 kWh of heating electricity, especially since sunny days are often followed by cold nights. On such days, we feed in 40–50 kWh from our 12 kWp system facing south.Can't you set the heat pump’s daytime temperature to 22–23 degrees Celsius (72–73°F) and use the electricity to heat? Then lower it to 19–20 degrees Celsius (66–68°F) at night, so the heat pump runs very little and the indoor temperature drops slightly. This way, you basically use your house as a thermal storage. Give it a try.Similar topics