A grid-tied solar PV system is a power plant that is connected to the utility grid and uses electricity from both the solar system and the utility grid.
These systems do not have to meet all of the electricity demands of the consumer electrical load. If needed, the load can draw energy from the grid at times (such as on cloudy days or at night) when the system is not generating electricity as per demand. Likewise, if energy generated is more than required, the surplus power generated can be exported to the utility grid.
These systems are connected to the main utility grid supply panel of the consumer facility and are designed to generate power when the utility grid is available (figure). In case of grid failure (blackout) or fluctuation outside permissible limits, the system stops working immediately and isolates itself from the grid. These systems are cheaper than battery-based solar power systems as there is no battery backup included, hence reducing the overall cost of the system.
The working of a grid-tied solar PV system is explained in the video, below.
Video by: MaXolar Energy (YouTube Channel)