Solar is unreliable and areas having low solar insolation, cloud or forest cover of tropics or equator, long nights of winter at high latitudes are not suited for solar energy. Land area is also a constraint and floating solar panels have to be installed over big water bodies like lakes and rivers or the sea in areas having high annual solar insolation to cut down on evaporative loss of water and save water for summer, area having no cloud nor forest covers and areas having long days or at least equal duration day like in tropical climates. Desert regions of Mohave, Thar, Arabian desert, desert nations of South America can use concentrated solar power plants.
Daily solar insolation can vary from season to season, from coastline to interiors, from equator to higher latitudes, from sea-level to high altitudes.
In many tropical and equatorial regions, there is cloud cover and cover of tall green forests prevent exposure of sun to the ground..
In residential and office buildings or high-rise towers, solar panels have to be installed on water tanks located on the terrace.