[adrianmonk]

Hopefully nobody thinks "I'll save even more if I get two!" and plugs them both into the same circuit.

Perhaps they could somehow detect each other and shut off.

[cenamus]

I think that's the reason why the total allowed panel power is only 800W, any more than that and you have to get it properly installed. At least that's ~ the way it is in Austria, it's also pretty easy to check whether you have ~800 or way more hanging on off your balcony.