Why is solar energy not your main source of energy?

Major draw back for Solar energy especially in Photo Voltaic type is the cost. With progress efficiency, the cost per unit still keep rising. A solar thermal plant in alternative can be made at reasonably cost competitive but was limited to economy of scale to be in a large size.
Both Photo Voltaic or Solar Thermal plant also share common draw back on energy storage. Solar thermal can only operated during day time and not work well with cloudy sky so it require power back up over the night or cloudy day. Storing electricity using battery is very expensive. Solar thermal could store energy in the form of molten salt (thermal energy storage) but that is only for short term.

If the solar energy plant would be put to use in large scale, it would require a back up power plant either from Hydropower, Biomass power, geothermal power or a nuclear power.