The important part is the isolation. The fact that it also transfers to local power is important to the user, irrelevant to the power company. The power compa

The important part is the isolation. The fact that it also transfers to local power is important to the user, irrelevant to the power company. The power company only cares that there no failure mode that can cause local generation to feed back onto the line. Whether it's a transfer switch, a local inverter that requires line power to operate or some other such system is irrelevant to them.