We received a quote from the electrician for a 10 kWp photovoltaic system. However, I am wondering whether investing in a 10 kWp system is really cost-effective or if a smaller system might be sufficient. Our four-person household consumes around 4,500 kWh in our rented apartment without a heat pump. In our planned single-family house (140 m² (1,507 sq ft), KfW 55 standard), there will be an air-to-water heat pump and possibly an electric car in the future. I am not familiar with the energy consumption of heat pumps, but wouldn’t 8 kWp or even less be enough? We do not want to feed electricity back to the grid, and the feed-in tariff is not a reason for us to choose a larger system.
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MeinHaus451 Feb 2022 16:03Stefan001 schrieb:
10 kWp, 18,000 gross. Storage 8 kWh, 4.5 k gross.
It might be worth mentioning that the 10 kWp system is equipped with individual power optimizers. This might somewhat justify the price. Is it only 22.5k or is labor time added as well?
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Deliverer1 Feb 2022 16:09Stefan001 schrieb:
equipped with individual power optimizers. These are almost always unnecessary, expensive, and make the system more prone to faults. They should only be used in extreme roof situations.For the electricity consumption, I would consider about 12 kWp with a 15 kW battery storage.
Without the battery, the self-consumption would be too low. If an electric car is going to be added, I would even install more than the 12 kWp.
I read today that in Germany the first modules from Trina Solar with 670 watts per pump are supposed to be available. That is certainly impressive.
Without the battery, the self-consumption would be too low. If an electric car is going to be added, I would even install more than the 12 kWp.
I read today that in Germany the first modules from Trina Solar with 670 watts per pump are supposed to be available. That is certainly impressive.
Durran schrieb:
that in Germany the first modules from Trina Solar with 670 heat pump should be available. That is certainly impressive. All modules over 2 sqm (21.5 sq ft) may only be installed outdoors in Germany and are not approved for roof mounting; in most cases, these are limited to around 400 W max.
The battery storage should be sized to cover overnight consumption. It is expected to be charged mainly during the day from April to October. During the remaining four winter months, the battery will hardly be charged at all since the electricity generated during the day can be used immediately. In the summer months, more electricity is generated during the day than can be consumed.
Assuming a continuous overnight consumption of 300 W (in my opinion relatively high), 12 hours of backup would require about 3.6 kWh of storage, so for a single-family home I would consider installing a 5–6 kWh battery.
Regarding electric vehicles, "intermediate storage" in the home battery does not make sense in my view. To store enough energy for 100 km (62 miles) of driving, you would need around 20 kWh of storage including losses, which involves significant costs.
If a heat pump is used, it consumes much more energy in winter than the photovoltaic system can supply anyway. Overall, a large battery rarely makes financial sense when the costs are taken into account.
Stefan001 schrieb:
10kWp, 18k gross. Battery 8kWh (8 kilowatt-hours) 4.5k gross
Maybe worth mentioning that the 10kWp system is equipped with individual power optimizers. That might somewhat justify the price.For a 10kWp system, the price should be around 1300–1400 EUR gross to be reasonable. Anything else, especially significantly more expensive, is not appropriate.
The power optimizers cost about 50 EUR each (around 30 units in your case?), so this does not really justify the higher price.
I think there was something else that was good about the individual power optimizers.
I don’t remember exactly, but I believe one supplier mentioned that even without shading, it can be beneficial because you can combine different roof sides into one string, and I think I even needed a second inverter without them (with full capacity, 4 roof sides).
Does that sound plausible? If not, it’s possible that I’m misremembering.
I don’t remember exactly, but I believe one supplier mentioned that even without shading, it can be beneficial because you can combine different roof sides into one string, and I think I even needed a second inverter without them (with full capacity, 4 roof sides).
Does that sound plausible? If not, it’s possible that I’m misremembering.
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