They don't need that kind of control, as evidenced by the fact that this kind of control is largely absent today for residential-scale grid-tied solar installations.

The way it works today for common residential grid-ties is this:

1. Is grid up? Y/N

2. If Y, then supply excess locally-generated power to grid. (Someone will implicitly use it.)

3. If N, then turn off connection to grid. (Nobody's home and we don't want to hurt anybody.)