ᐅ Quote for photovoltaic system including battery storage – storage yes/no?
Created on: 8 Sep 2024 16:53
H
haus_bau2025
Hello everyone,
My wife and I are currently planning to build our single-family home of about 140 m2 (1,507 sq ft) and are considering whether to build it to KfW 40 standard or not (mainly for cost reasons). We have received an offer from our construction company for a photovoltaic system with 6 kWp and a high-voltage battery from Varta with 6.5 kWh (6.5 kWh) storage capacity, costing around 18,000 euros. Since the battery alone costs nearly 6,000 euros, and I recall reading here in the forum that many people reject a battery because a) it is too expensive and b) it would be better to invest in additional photovoltaic modules instead, I wanted to ask how you would approach this situation. The plan also includes installing an air-to-water heat pump with central, decentralized, or controlled mechanical ventilation (we are still considering these options as well).
1.) Would you remove the battery and replace it with more photovoltaic modules? If yes, how much kWp capacity would you recommend for a single-family home built to KfW 40/55 standard with "normal use," i.e., occasional home office?
2.) Or would you keep the battery and increase the photovoltaic system capacity with additional modules?
Do you have any other ideas or suggestions regarding what we should pay attention to in connection with the photovoltaic system?
My wife and I are currently planning to build our single-family home of about 140 m2 (1,507 sq ft) and are considering whether to build it to KfW 40 standard or not (mainly for cost reasons). We have received an offer from our construction company for a photovoltaic system with 6 kWp and a high-voltage battery from Varta with 6.5 kWh (6.5 kWh) storage capacity, costing around 18,000 euros. Since the battery alone costs nearly 6,000 euros, and I recall reading here in the forum that many people reject a battery because a) it is too expensive and b) it would be better to invest in additional photovoltaic modules instead, I wanted to ask how you would approach this situation. The plan also includes installing an air-to-water heat pump with central, decentralized, or controlled mechanical ventilation (we are still considering these options as well).
1.) Would you remove the battery and replace it with more photovoltaic modules? If yes, how much kWp capacity would you recommend for a single-family home built to KfW 40/55 standard with "normal use," i.e., occasional home office?
2.) Or would you keep the battery and increase the photovoltaic system capacity with additional modules?
Do you have any other ideas or suggestions regarding what we should pay attention to in connection with the photovoltaic system?
I was fortunate to be able to do my photovoltaic system as a DIY project. I was not willing to pay those sky-high prices and then not be able to freely choose almost 99% of the hardware.
I ended up building a Victron system, where a battery storage is mandatory, and backup power is included for free. You also have to consider high and low voltage separately here.
Since we are away during the day and only cook, do laundry, etc., in the evening, the battery is usually at about 15% by the next morning. The system started operating at the beginning of July and had around 25 charge cycles in the first two months. I am curious to see how a full season will look.
Overall, my 22.88 kWp (kilowatt-peak) photovoltaic system + 19.2 kWh (kilowatt-hour) battery + masonry enclosure for the equipment + split air conditioning cost me about €960 per kWp (approximately $960 per kWp).
I took a very pragmatic approach when calculating. Electricity payments before photovoltaic were €293 and after photovoltaic €50. That means a monthly saving of €243, excluding any Renewable Energy Act subsidies. The system pays for itself after about 7-8 years.
I ended up building a Victron system, where a battery storage is mandatory, and backup power is included for free. You also have to consider high and low voltage separately here.
Since we are away during the day and only cook, do laundry, etc., in the evening, the battery is usually at about 15% by the next morning. The system started operating at the beginning of July and had around 25 charge cycles in the first two months. I am curious to see how a full season will look.
Overall, my 22.88 kWp (kilowatt-peak) photovoltaic system + 19.2 kWh (kilowatt-hour) battery + masonry enclosure for the equipment + split air conditioning cost me about €960 per kWp (approximately $960 per kWp).
I took a very pragmatic approach when calculating. Electricity payments before photovoltaic were €293 and after photovoltaic €50. That means a monthly saving of €243, excluding any Renewable Energy Act subsidies. The system pays for itself after about 7-8 years.
Buchsbaum066 schrieb:
If only, if only.
You first need to get approval from the grid operator for the 50 kWp system. That’s not so easy nowadays. Unfortunately, the power grids in Germany are quite outdated.
And if you want to upgrade later, you have to start all over again. Data cables, smart meters, upgrading the meter cabinet, installing storage, and also a new inverter. Filling the entire roof just doesn’t make sense.
It only really pays off for large installations with direct marketing. No problem at all to get that approved. I wouldn’t even have to modify my meter cabinet or meter.
My house connection already has 3x175A (3x175 amps). I would also build a battery storage system and use everything myself.
It wouldn’t even be about profitability for me.
B
Buchsbaum06612 Sep 2024 21:06rick2018 schrieb:
No problem getting that approvedI'm glad it works out for you. Unfortunately, in many parts of Germany it’s not possible. It always depends on where you live.
Try not to make it too complicated. If you’re unsure about adding a battery storage system, leave it out for now and choose an inverter that can support a battery later. Battery prices are currently quite low, and there will likely be developments over the next few years.
I can share our experience. We have an almost 10 kWp system without storage. In summer, it delivers nearly 9 kW at peak, and we consume roughly half of that with all our devices. I’m not including the electric car here. So, in summer, our battery would be full all the time if we had one.
In winter, the system produces around 2 to 4 kW when sunny, depending on the time of day. As soon as a cloud appears, output quickly drops to 1 to 2 kW. With more clouds, it can fall to just 0.2 to 0.4 kW. At that point, it’s not very useful. The battery either stays idle or is empty after at most two hours.
You can see that a battery is really only useful in summer.
There are two practical options:
1. A small battery of about 4 kWh. This will make you quite self-sufficient in summer and help save any occasional surplus energy produced in winter.
2. Wait a few more years to buy a battery until second-life car batteries become available. For the past few years, an industry has been developing that buys these batteries and refurbishes them for home use or commercial applications as large storage systems. You would then have a seasonal storage solution that charges during summer and can be used in autumn and partly in winter. Currently, these batteries are expensive, but that should improve over time.
I can share our experience. We have an almost 10 kWp system without storage. In summer, it delivers nearly 9 kW at peak, and we consume roughly half of that with all our devices. I’m not including the electric car here. So, in summer, our battery would be full all the time if we had one.
In winter, the system produces around 2 to 4 kW when sunny, depending on the time of day. As soon as a cloud appears, output quickly drops to 1 to 2 kW. With more clouds, it can fall to just 0.2 to 0.4 kW. At that point, it’s not very useful. The battery either stays idle or is empty after at most two hours.
You can see that a battery is really only useful in summer.
There are two practical options:
1. A small battery of about 4 kWh. This will make you quite self-sufficient in summer and help save any occasional surplus energy produced in winter.
2. Wait a few more years to buy a battery until second-life car batteries become available. For the past few years, an industry has been developing that buys these batteries and refurbishes them for home use or commercial applications as large storage systems. You would then have a seasonal storage solution that charges during summer and can be used in autumn and partly in winter. Currently, these batteries are expensive, but that should improve over time.
D
Dahlbomii20 Sep 2024 16:49Evolith schrieb:
So you see, the battery only really makes sense during the summer.Unfortunately, that’s the downside of photovoltaic systems in general: they produce the most when the demand is at its lowest, both daily and annually. Smoothing this out on a small scale is still not economically viable.
On paper, under ideal conditions such as no snow cover and so on, your system should generate about 450 kWh in December, realistically probably less due to degradation. That equals about 15 kWh per day. With a typical annual electricity consumption of 3,500 kWh, this amounts to 291 kWh per month, although consumption tends to be higher during the winter months. This would just about cover it. For a significant portion of the generated energy to be stored in the battery, neither a heat pump nor an electric vehicle should be connected. The battery only becomes interesting once the system is really large and the cost of batteries drops close to zero, allowing for a much larger capacity to serve as a buffer for more than one night.
Similar topics