[jefftk]

This is a great question! In our case, in MA, rooftop solar was only economically viable because of two subsides:

* New metering, where the power company has to act as our battery for free. Even if we produce more than we're using, which we do most afternoons when few of us are home, each kWh we send into the grid reduces our bill as the end of the month by one kWh.

* SREC II subsidies, where we just get money per kWh we produce.

Both of these are available to homeowners but not to commercial producers.

(We also got a tax credit, but it's possible that companies also get similar credits.)