The system I am about to describe here
is called a grid-tie system. There are no batteries. If the solar
panels produce more power than what the home is using, power will
back-feed into the utility's power grid. If you have a bidirectional
meter (see NetMetering below) then your meter will literally run
backwards when this occurs. From a logical standpoint, the grid now performs the same
role a bank of batteries would perform. The grid stores unused energy
by day and gives that energy back at night.
Also note that all grid-tie solar
systems have a safety feature in them that disables power from the
panels if power from the utility grid goes down. That's right. It
means you cannot use your solar panels if the power from your utility
company is out. This is a safety feature. We don't want to back-feed power onto the grid when the grid is down.
