ᐅ Planning Photovoltaic Systems – Potential Retrofit of Battery Storage
Created on: 12 Feb 2018 10:04
J
jx7How do you plan a photovoltaic system that might later be equipped with a battery storage, if rising electricity prices and falling battery prices make this economically viable?
Option 1:
- Design and plan the system including storage, but simply leave out the battery for now.
- Very simple retrofit option: only connection of the battery required.
- However, as long as no battery is added, the system is oversized because there are too many panels on the roof.
Option 2:
- Design and plan the system including storage, but leave out the battery and install fewer panels on the roof.
- Retrofit option available by adding the battery and installing additional panels.
Option 3:
- Initially design the system completely for operation without storage (saves costs).
- Retrofitting later is somewhat more complex.
Where do you see the best option when weighing the three cost factors:
- Installation costs of the system (without storage)
- Economic efficiency of the system operating without storage
- Possible costs of converting to operation with storage
4-person household, gable roof surfaces facing west and east, household electricity consumption 5200 kWh per year, geothermal heat pump
Option 1:
- Design and plan the system including storage, but simply leave out the battery for now.
- Very simple retrofit option: only connection of the battery required.
- However, as long as no battery is added, the system is oversized because there are too many panels on the roof.
Option 2:
- Design and plan the system including storage, but leave out the battery and install fewer panels on the roof.
- Retrofit option available by adding the battery and installing additional panels.
Option 3:
- Initially design the system completely for operation without storage (saves costs).
- Retrofitting later is somewhat more complex.
Where do you see the best option when weighing the three cost factors:
- Installation costs of the system (without storage)
- Economic efficiency of the system operating without storage
- Possible costs of converting to operation with storage
4-person household, gable roof surfaces facing west and east, household electricity consumption 5200 kWh per year, geothermal heat pump
Why do you think you need more panels if you have a battery?
There are basically two approaches:
- The system pays for itself, so you fill the roof with as many panels as possible. More panels mean higher revenue (greater yield).
- The system is optimized for personal needs, meaning it is adapted to the household’s electricity consumption (higher self-consumption).
The battery initially doesn’t really affect this and should in any case be sized according to personal consumption, otherwise an expensive battery will remain unused most of the time. Just ask for a system that can have a battery added later; this should be possible with (almost?) all systems without much effort.
Much more important is calculating the expected yield and considering certain thresholds from a tax perspective, especially 10kWp and 30kWp.
There are basically two approaches:
- The system pays for itself, so you fill the roof with as many panels as possible. More panels mean higher revenue (greater yield).
- The system is optimized for personal needs, meaning it is adapted to the household’s electricity consumption (higher self-consumption).
The battery initially doesn’t really affect this and should in any case be sized according to personal consumption, otherwise an expensive battery will remain unused most of the time. Just ask for a system that can have a battery added later; this should be possible with (almost?) all systems without much effort.
Much more important is calculating the expected yield and considering certain thresholds from a tax perspective, especially 10kWp and 30kWp.
Thank you for your response!
I thought that nowadays the system size is always adjusted to self-consumption because selling electricity alone is no longer profitable due to the low feed-in tariffs. I also read that with a storage system you can cover about 70% of your own consumption, while without storage it’s around 30%. Neighbors have a photovoltaic system without storage that is half the size of the one currently proposed to us with storage. Based on this, I assumed that photovoltaic systems without storage are always designed smaller than systems with storage.
In the meantime, I have learned that in my case it makes sense to install the full number of panels at once to avoid having to go back on the roof a second time for installation when adding the storage later.
I have also learned that for direct feed-in, you need an inverter costing about €1800, which could be avoided if you install the storage system right away.
I am aware of the 10 kWp threshold, at which point the Renewable Energy Act surcharge applies, making the system unprofitable.
I thought that nowadays the system size is always adjusted to self-consumption because selling electricity alone is no longer profitable due to the low feed-in tariffs. I also read that with a storage system you can cover about 70% of your own consumption, while without storage it’s around 30%. Neighbors have a photovoltaic system without storage that is half the size of the one currently proposed to us with storage. Based on this, I assumed that photovoltaic systems without storage are always designed smaller than systems with storage.
In the meantime, I have learned that in my case it makes sense to install the full number of panels at once to avoid having to go back on the roof a second time for installation when adding the storage later.
I have also learned that for direct feed-in, you need an inverter costing about €1800, which could be avoided if you install the storage system right away.
I am aware of the 10 kWp threshold, at which point the Renewable Energy Act surcharge applies, making the system unprofitable.
T
toxicmolotof12 Feb 2018 14:02If possible, keep it under 10kWp.
You can either install a storage system now along with appropriate inverters (sized according to your energy consumption plus a small buffer), or you can skip it altogether and only make changes again when the inverter fails.
You can either install a storage system now along with appropriate inverters (sized according to your energy consumption plus a small buffer), or you can skip it altogether and only make changes again when the inverter fails.
Correct, adding later is not impossible, but it requires some planning because the different segments need to be coordinated.
A very general calculation, to give an idea:
- A total system output of 10 kWp costs about €12,000 (all in) as a complete package
- The yield depends on location and orientation, roughly 8,000–9,000 kWh
- The feed-in tariff is currently 12.5 cents, which amounts to €1,000 for 8,000 kWh
- Without self-consumption, the system pays for itself after about 12 years; any self-consumption reduces this payback period
... of course, the tax aspect is not considered here, but neither is self-consumption. As a rough guideline, this shows that the roof should simply be fully utilized if you decide to install photovoltaic panels (systems between 10 and 15 kWp are less favorable for the reasons mentioned above).
A very general calculation, to give an idea:
- A total system output of 10 kWp costs about €12,000 (all in) as a complete package
- The yield depends on location and orientation, roughly 8,000–9,000 kWh
- The feed-in tariff is currently 12.5 cents, which amounts to €1,000 for 8,000 kWh
- Without self-consumption, the system pays for itself after about 12 years; any self-consumption reduces this payback period
... of course, the tax aspect is not considered here, but neither is self-consumption. As a rough guideline, this shows that the roof should simply be fully utilized if you decide to install photovoltaic panels (systems between 10 and 15 kWp are less favorable for the reasons mentioned above).
At the moment, I wouldn’t worry about an energy storage system. Profitability is still far off given the current prices, and this won’t change in the coming years. Even from a purely ecological perspective, it’s somewhat self-deceptive, as manufacturing the storage system is certainly less environmentally friendly than the electricity from the grid.
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