The reason for the high cost is the labour intensive process of making the cells, even though the silicon itself itself is found in abundance in the form of sand. With improved production methods and mass production the cost of photovoltaic cells would decrease. Fossil fuels increase in cost as the resource becomes more scarce or if the producing nations slow production to increase the cost. At some point, the costs of the two methods of energy conversion will intersect. It is estimated that over 90 percent of energy used is from fossil fuel and that this source will be depleted within 100 years.
Fossil fuels cause pollution, heating the atmosphere and water systems.
The by-products causes smog and fallout into the lakes. It is estimated that 15 minutes of the actual sun's energy reaching the earth, could supply sufficient energy for a whole year. The average solar energy striking the roof of a typical house is 10 times its annual heat demand. Photovoltaic systems should be used at the present time, to demonstrate the useful applications such as supplying power to remote sites where it would be too expensive to provide transmission lines or diesel generator systems. This interest, may provide support for more research and development to improve the efficiency and reduce the cost per unit of power produced.