There are two different systems for electricity producing from solar energy: On-Grid and Off-Grid systems.
On-Grid system is useful and cheaper than Off-Grid system. This system doesn’t need any accumulator like battery and this makes it cheaper. System is connected to electricity network to sell excessive electricity produced by system. This system needs permission from local authority in accordance with laws and Agreement with electricity supplier.
Off-Grid system is an independent system that you can have in your houses. We may explain the system simply as follows Off-Grid components simply are PV panels, Charger Controller, Batteries and AC Inverter. The efficiency of a PV panel is between 15% and 20%. For Bucharest we can use maximum capacity of 1292 kWh/m² - year. Panel capacities is given by producers under approximate insolation value of 1000W/m². For a 5 kW average daily electricity usage and 5 hours daily sunshine duration in winter time, we need a set as 4 piece 250 Wp panels, 10 kW capacity batteries, charger controller and DC inverter. Detailed calculations are necessary for different applications.
PhotoVoltaic solar systems 100-500kW
PhotoVoltaic solar systems > 500kW