That's because putting solar on rooftops makes little economic sense. The overhead in terms of installation cost was relatively insignificant when PV panels cost 20 times as much - as they did 15 years ago. These days, the cost is swamped by installation costs.
These days, the only place it makes sense to put PV is flat on unused or unproductive land. The 95% drop in PV panels means that it is no longer economic to bother with mechanical tracking in solar farms. Integrating panels into a domestic roof destroys the incredible cost advantages PV has over alternative power sources.
These days, the only place it makes sense to put PV is flat on unused or unproductive land. The 95% drop in PV panels means that it is no longer economic to bother with mechanical tracking in solar farms. Integrating panels into a domestic roof destroys the incredible cost advantages PV has over alternative power sources.