That's how traditional (not plug in) panels are connected. The problem is - you need to route a cable from window/balcony to the panel (which may be located out

That's how traditional (not plug in) panels are connected. The problem is - you need to route a cable from window/balcony to the panel (which may be located outside an apartment in a hall) and if you want to hide the cable in walls it becomes expensive. With plugin you can use closest to the panel socket. En easier solution is a clamp power meter on a socket circuit connected to the inventor via z-ware / zigbee so the inverter can see total socket circuit load and limit own power as a protective measure (at which point a circuit breaker likely will be tripped).