Did you guys catch Elon's description of how people would use a Powerwall in a backup scenario at the shareholder meeting? Most existing backup systems (either via a generator or a hybrid solar/battery system) have a "critical load" electrical panel. When grid power goes down, a transfer switch trips, isolating the critical load panel from the grid. The critical load panel is then fed power from the backup power source. The idea being that the backup power source can't feed the entire house, so only critical loads are fed (like freezers, refrigerators, some lights, etc.). However, when you have a solar panel system, the solar system typically generates more power than the entire house needs during the day. So Elon mentioned in passing today, a different way to arrange critical loads. He suggested that people with solar panels and an appropriate number of Powerwalls would instead have a non critical load panel which would be turned off in a power outage giving power to everything else in the house. So only power to non essential high power devices like air conditioners would be turned off. I picked up on this because this is exactly what I'm thinking of doing in the new house I'm going to build. In fact you could theoretically go a step further and have an energy monitoring program turn on and off non essential loads during power outages depending on the available power available from the solar/battery systems.