Consultation for photovoltaic systems

We have a consumption of 3900 kWh, of which 975 kWh come from the grid.

Battery BYD 5.2 kWh: 1510 kWh charged, 1174 kWh discharged. 290 full cycles. Efficiency 78%.
Okay, the inverter is incorrectly sized, my mistake (5 kW instead of 3.2 kW).
8600 kWh yield from a 10 kWp SSW system on a flat roof (5°).

If I only consider the discharge energy, then that is 1174 kWh * 0.285 cents per kWh = €330 savings.
The loss of 1510 kWh * 0.10 cents per kWh = €151 feed-in tariff (+ the standby consumption when the battery is not charged) is opposed to that.
I wouldn't know how I could justify the investment of €5300?

The storage was free by a happy coincidence. Otherwise, it would never have paid off.

Edit: If I had invested the €5300 gross in additional panels, that would result in an increase of 4 kWp, which would be about €344 at 860 kWh per kWp/year. Definitely better invested.

And that at 290! Full cycles. Another amazing value here in the thread. I read such numbers from practice once a week. If someone even reaches around 200 cycles, they are already congratulated! ;-)

Full cycles are calculated from charging energy/storage size or do I have to read them off? :rolleyes: Is the number really unusually high?

Full cycles are calculated from charging energy/storage capacity or do I have to read them off? :rolleyes: Is the number unusually high?

It was unknown to me until just now - learned something again :) So for me it's 1,657 / 9.8 = 179. So bronze medal with currently three participants :D

Yes

Full cycles are calculated from charging energy/storage capacity or do I have to read them off? :rolleyes:

Strictly speaking, the power loss that did not contribute to charging must also be deducted. Most systems determine the number themselves, but I do not know exactly according to which criteria. Roughly, however, your calculation is correct.

Then for me it's 1,657 / 9.8 = 179.

For a 10 kWh battery, that's really decent. And the goal isn't really to achieve a high number of cycles. It's just the only way to break even, and you can tell from it whether the battery size matches the photovoltaic system and consumption. But an unused kWh is still always cheaper than one unnecessarily drawn through the battery.