They can withstand severe weather conditions including snow and ice. They consume no fossil fuels - their fuel is abundant and free. They can be installed as modular building blocks - as your power demand increases, you may add more photovoltaic modules. Solar electric is not cheap, and does not make sense for all applications. It makes sense for remote sites that are too far from power, or where the power is too unreliable.
Examples are bus stop shelters, storage yard lighting, rail signals, and cell phone transmitters.
It does not make sense in a typical residence or business that is connected to regular grid power. The installation costs are far too high, and the payback is 15 to 25 years, assuming no maintenance. If you have an electric cook stove, air conditioning, and an electric hot water heater, forget it, or switch to gas. That includes the complete system with CP controller. However, that can vary considerably depending on the actual sun-hours in your location, and is more for small systems due to the fixed costs of the controls.