Balcony solar battery calculator
Work out whether adding a battery to your balcony solar system is worth it for your household – and how much extra it would actually save.
A balcony solar system – Balkonkraftwerk in German, and the word you will see on German shop listings and paperwork – is a small plug-in solar setup for a balcony, terrace or garden. Whether a battery pays off on one depends mainly on how much of your solar electricity would otherwise go unused, and on what the battery adds to the price. The number that decides it is therefore the additional saving of the battery compared with the same system without one – not the total saving of the system. Two households with identical panels can end up with opposite answers.
Your details
When does a battery pay off on a balcony solar system?
Solar electricity is generated around the middle of the day. In many households it is used in the morning and in the evening. Whatever is generated in that gap and not needed straight away flows into the grid, and on a balcony system in Germany that generally earns little or nothing. That unused surplus is the raw material a battery works with: it shifts it into the evening. If there is little surplus to begin with, there is little for a battery to rescue, however good the battery is.
Four things decide the answer:
- Your daily routine. If you are out during the day, more electricity goes unused and a battery has more to capture. If you work from home, you often consume the solar electricity as it is produced, and less is left over.
- How much goes unused. A large system in a small household produces more surplus than a small system in a large one.
- Your electricity price. Every kilowatt-hour the battery delivers in the evening is worth exactly as much as the electricity you then do not have to buy.
- The price of the battery. This is the additional investment that has to earn its keep – and the reason the same battery can move from "not worth it" to "worth it" as prices fall.
Why a blanket recommendation is not enough
Because the answer sits with the household, not with the product. Payback times quoted for balcony solar batteries vary widely, and that is not a contradiction: it follows from different assumptions about consumption, daily routine, electricity price and purchase cost. A figure that is right for a household at home all day is simply a different figure for a household that leaves at eight in the morning.
So this page states no universal payback time. It calculates one for the details you entered above.
How stromFit works this out
The calculator on this page calls the same simulation as the full stromFit analysis: location-specific solar yield for your postcode, an hourly household load profile, the economics without a battery, and then the battery simulation with charging and discharging across the year. The battery verdict comes out of the comparison between those two runs – it is not derived from a rule of thumb.
Deliberately conservative: no feed-in tariff, no assumed electricity price rises and no subsidies. Prices come from complete systems that can actually be bought in Germany rather than from an average. Where a mandatory part has no known price yet, the figure is shown as a lower bound rather than treated as zero. The individual assumptions are set out under methodology.
A battery, or just the panels?
Both are legitimate outcomes. A balcony solar system without a battery usually pays for itself faster, because it costs less to buy. A battery raises the annual saving but costs extra, so it has to carry itself out of its own additional benefit. stromFit calculates the two separately and says so plainly when the honest answer is "no battery".
If you want the payback of the panels on their own, use thebalcony solar payback calculator. For background on how these systems work in Germany, see the guide tobalcony solar in Germany. For the exact recommendation including matching systems, start the stromFit analysis.