Sorry but the first part is just incorrect. They are indeed simple, which is why they do feed back into the grid. Not feeding back would take effort and additional hardware. But you’re not being paid for what is fed back into the grid, making it free energy for the electricity provider (see my last paragraph below).

To explain it a bit: electrically, the external grid and the grid in your home are simply connected (assuming the breakers are closed). If you use more than you produce, whatever is missing “flows in”. If you produce more than what you’re currently consuming, whatever is left over just flows out into the grid. Even if this if obviously simplified, this “just happens” with no effort required, but the amount that flows in or out is easy enough to measure (which is what the electricity meter does that sits between the big grid and the one in your house). If you want to actually make sure you don’t feed back into the grid, you would constantly need to monitor if anything is flowing in our out, and compensate with reduced (or increased) production. Even full size solar installations can’t do this with perfect precision, even if you tell them to: you can only react to the flow you see coming in/out, if you turn a large heater quickly on and off and on and off, it won’t have time to react quickly enough.

For the longest time (until early 2023 I think), you had to ask permission from your electricity network operator (is that the correct term? “Netzbetreiber”), because they would only allow you to install it if you had at least a semi-modern electricity meter that won’t turn backwards. Because balcony solar always feeds into the grid, you’d effectively be paid the same per kWh as what you’re paying yourself. You would effectively use the grid as a infinitely large battery.

As I’d replied to a sister comment of yours, I didn’t even consider that the author could be talking about actually available power, so that’s on me. I did go re-read it and I really don’t think that’s how it is meant though. I do think they are just ignorant on this point.

That being said, “balcony solar” isn’t limited to 800 W in panels. It’s limited to an 800 W inverter, but 2 kW for the panels. So you can have quite a bit more capacity in solar compared to the inverter, which also means that worse weather impacts you less. When you got a full sunny day, you can have the full 800 W for much longer, if not most of the day, as it’ll essentially be limited further down the chain. On the other hand I do think the most common size actually installed is much closer to also only have 800-900 Wp (basically 2 panels), which is the most commonly offerend (and presumably sold) kit size.

We also have roughly 8 kWp installed, and obviously on cloudy or dark winter days we’re an order of magnitude away from that number. There are days where we break 40 kWh in production, and there are days where we barely make it to 1 kWh. That low is very rare, even in winter or on dense, cloudy days, so I’d consider 4 kWh a more realistic minimum value. We have relatively detailed monitoring of most (relevant) consumers, which is why I have a somewhat good idea of how much our house consumes in practice. Before this full size installation, we had a 2 panel balcony solar “test setup” for quite a while. It was actually quite a (positive) surprise on how many days we essentially covered the majority of our daylight usage with these panels. Obviously not for the big-ticket consumers, but even a washer/dryer will be mostly covered.

Ok, fair point. But even considering that as an option, it’s not at all how I read that paragraph even if I actively keep this in mid.