What is the difference between on-grid(grid-tied) solar system and off-grid solar system?

What is the difference between on-grid(grid-tied) solar system and off-grid solar system?

The simple answer to this is that on-grid solar systems can send the electrical power generated by the PV to the utility power grid while the off-grid solar systems can not.

1.On-grid (grid-tied) solar system
The main components for on-grid system includes solar panel,solar charge controlller and on-grid inverter,but without battery.
In the on-grid solar system,the electrial power generated by the solar panels will send the the grid power directly through the on-grid inverter.In that case,all the power generated by the PV will send to the grid power to achieve revenues,and this power cannot supply to your own electrical load,nor can it be used as a backup power.

2.Off-grid solar system
The main components for off-grid system includes solar panel,solar charge controller,battery and off grid inverter.The off-grid system must include battery.
In the off-grid solar system,the electrial power generated by PV will send and storage to the battery directly through the solar charge controller.And the electric energy stored in the battery is converted to AC power by the off-grid inverter and supplied to the load for use.In that case,all the power generated by the PV will supply to your own electrical load and storaged in the battery,cannot sent to the grid power.The off-grid solar system can be used as a backup power also.

How to choose?
If you want to achieve revenues,you can choose on-grid solar system;If you want to use the PV power to your own house to save money and get backup power,you can choose off-grid solar system.