In the last decade the proliferation of solar Photovoltaic has cause the
price of the panels to be cut to a fourth of what they were in 2010. So
the panels now are a commodity, rather than the big cost driver of the
total system that they use to be. A typical mid range quality solar PV
panel rated at 320 watts and will cost between $200. So if you add all
the other components, labor , design, permits, etc, as a rule of thumb
assume a ground mounted system will run about $1100 per panel and a
roof mounted system is about $900 a panel.