SOLAR POWER

Solar power is the conversion of renewable energy from sunlight into electricity, either directly using photovoltaics (PV), indirectly using concentrated solar power, or a combination.

Yes, solar power work on cloudy days but the efficiency is not performing well as on a sunny day.

The best way to figure out is to check the total energy consumption from the last 12 month in your electricity bills.

Solar panels collect sunlight and convert sunlight into electrical energy, the electricity would be stored in batteries. 

The solar system consists of Solar panels, a controller, a battery, and an inverter. Your cost is based on your electricity need. For example in the 400W solar system. 500 bucks for the 400W solar panel, 150 bucks for the MPPT solar, a 12V/100 ah battery for about 500 bucks, and the 200 bucks for 1000W, and maybe some extra mount tilt or connect cables for about 150 bucks. 1500 bucks in total.

The efficiency of solar energy is range from 15% to 23%. Many factors will influence the efficiency, such as panel materials, temperatures, sunlight, etc.