Solar Power Systems used in residential and commercial loads can be distinguished as On-Grid and Off-Grid Solar Power Systems.
To understand the difference between On-Grid and Off-Grid Solar Power Systems we can refer to their respective definitions:
On-Grid Solar Power System
On-Grid Solar Power Systems as the name suggests are Grid Tied or On-Line Solar Power Systems where Solar Electrical Energy is used in conjunction with main electrical supply. Grid Tied Power Systems receive power from Solar Panels Setup and also regular electrical supply by companies.
There is a provision in this kind of Solar Power Plant to switch back and forth between Solar Supply and Regular Supply.
During the night time or when there is cloudy weather and Solar Panels aren’t generating enough electricity to serve electrical loads you can switch back to your regular supply.
Solar Panels produce DC electricity and hence they are connected to a inverter which converts DC to AC and serves residential or commercial load.
Net-metering services are becoming common now a day where users have to pay only for electrical usage that is done when Solar Panels are unable to deliver required power. If consumers generate more electrical power from Solar Panels than their regular load consumption then they can supply that extra power to Electrical Grid and they will be paid as per the tariff rates.
In an On-Grid Power System there is no option to save the electricity from Solar Panels.
Off-Grid Solar Power System
Off grid solar power system is same as on grid system but you can store electricity generated by Solar Panels in batteries here.
In an off grid solar power system Solar Panels are connected to Solar Charge Controllers which are connected to Solar Batteries to store Electricity.
Off-Grid Solar Power System may or may not be connected to electrical supply mains.
Solar Batteries are connected with electrical inverters to serve AC loads.
Technical Specification of Batteries, Inverters and Solar Panels depend upon the Electrical Load Consumption.
Conclusion: On-Grid Solar Power System is without any power saving device and serves electrical load On-line when Sun is bright and an Off-Grid Solar Power System can be used to serve the load online as well as save power in batteries for later use when sunlight would fade.