I am having trouble understanding your argument. Let us assume that a residential system uses enough photo-voltaic modules to generate as much power as is consumed on average (thereby creating a situation as you say, where excess power can be sold, or a power deficit can be filled by the grid). If I understand your argument correctly, you are saying that once grid-supplied power is cut, that "almost certainly nothing" in the house will work.

However, I don't understand why that would occur. The PV modules, in the presence of sunlight, are still generating power. Where does this energy go? This line of thinking conjurs up a couple of questions for me:

1. An alternative, stand-by form of power, such as a generator, can be substituted for grid power via a transfer switch. Why can't similar technology be used to switch the source of house power to the PV modules alone, isolating the grid?

2. Backup battery power is nice would be welcome in the event of a grid failure, especially at night. However, I don't understand why the inverter has to stand alone. Why can't a battery system be charged by the PV modules?