r/SolarState

After about nine months running a balcony solar system with battery storage, I finally sat down and did the full financial analysis. I want to share the real numbers because I think there's a lot of optimistic math floating around and not enough honest breakdowns.

My setup: two 400W panels on a south facing balcony in central Germany (Frankfurt area), mounted on the railing at roughly 30 degrees. The battery unit is a Jackery HomePower 2000 Ultra with the base 2 kWh storage, feeding into the apartment via Schuko plug at 800W. Total system cost was roughly EUR 1,350 after a small municipal subsidy.

Now, the generation numbers. From September 2024 through May 2025, I logged everything through the app. In the good months (April, May) I was pulling in about 3.2 to 3.8 kWh on clear days. In winter (December, January), that dropped to 0.4 to 1.1 kWh on most days, with some days producing almost nothing. My rough projection for the full year is somewhere around 750 to 850 kWh total generation. That is far below the "up to 2,400 kWh" figure you sometimes see quoted, but that number assumes perfect conditions with maximum panel capacity, which no balcony setup realistically achieves.

The self consumption question is where the battery actually matters. Without storage, I'd estimate my self consumption ratio would be around 30 to 40 percent, because I work from home only two days a week and most generation happens midday when nobody is using much. With the 2 kWh battery, I'm shifting a meaningful chunk of that solar energy into the evening hours when we actually cook, run the dishwasher, and watch TV. My self consumption ratio is closer to 70 percent now. That's the real value of the battery for someone who isn't home during the day.

So let's do the math. At roughly 800 kWh generated per year and 70 percent self consumption, that's 560 kWh I'm actually using instead of buying from the grid. My current electricity tariff is EUR 0.34 per kWh (Stadtwerke Frankfurt, nothing fancy). That means I'm saving roughly EUR 190 per year. The remaining 240 kWh that I feed into the grid earns me effectively nothing because my contract doesn't compensate for feed in at this scale.

EUR 190 per year against a EUR 1,350 investment gives me a payback period of just over seven years. And that's actually a somewhat optimistic calculation because I haven't factored in the standby consumption of the battery unit itself (about 3W continuous, which adds up to roughly 26 kWh per year) or any potential degradation over time.

For comparison, if I had gone with panels only and no battery (total cost around EUR 400 to 500 for a basic 800W kit), the self consumption would drop but the payback would be much faster. Roughly EUR 90 to 110 saved per year against a EUR 450 investment means payback in about four years. The battery nearly triples the system cost while roughly doubling the savings. Financially, the panels alone are the stronger play.

So why did I go with battery storage anyway? Partly because I wanted to maximize what I actually use rather than feeding energy into the grid for free. Partly because the idea of storing solar energy for evening use just felt right from a practical standpoint. And partly because I'm betting that electricity prices in Europe aren't going down anytime soon. If my tariff increases to EUR 0.40 or higher, the payback math improves significantly.

I'm not trying to discourage anyone. I genuinely enjoy watching the real time generation data and knowing that my evening coffee machine is running on solar energy I collected that afternoon. But I think it's important to be transparent that the financial case for balcony solar with battery storage is not a slam dunk at current prices, especially compared to panels alone.

I'd love to hear from others who've done similar calculations on their balcony setups. What electricity price are you paying, and what payback timeline are you looking at? I'm especially curious whether the financial case or the environmental motivation was the bigger factor in your decision.