http://en.wikipedia.org/wiki/Photovoltaic_system#Insolation_and_energy http://en.wikipedia.org/wiki/Photovoltaic_system#Insolation_... I'm taking the lowest va

http://en.wikipedia.org/wiki/Photovoltaic_system#Insolation_and_energy http://en.wikipedia.org/wiki/Photovoltaic_system#Insolation_... I'm taking the lowest value of 0.75 kWh per day. A quick look with google shows average yearly consumption per home is ~10000 kWh or 27.3kWh per day. So you would need about 36.5 m^2 for a home. That is about 6x6 meters and would fit nicely on a typical house, but probably not on a apartment building and much less on a skyscraper. I assert that the problem is in the cost of the cells, cost and storage problem of batteries(no power at night and not relying on other sources) and unawareness of the general population. I am not an expert on the this field and would gladly be corrected.