No, an inverter that syncs to the incoming power line. It just backfeeds a two pole breaker in your panel. The inverter will shut down when it senses no power from the utility.
There are of course all kinds of other schemes and some do use batteries, kind of like a UPS but these are not what you see in these residential solar installs.
By the way Sam, since you got me interested, driving around the neighborhood it looks like 10-12 panels is the norm even here when they could get twice as many on the roofs. Wonder why?
-Hal
