Distributed photovoltaic energy storage systems can be connected to the grid, but it is not an absolute requirement. The decision to connect a photovoltaic energy storage system to the grid depends on several factors, including the specific requirements of the user, local regulations, and the intended purpose of the energy storage system.

1. Grid-Connected Systems: Connecting a distributed photovoltaic energy storage system to the grid allows for the possibility of selling excess energy back to the grid, providing a source of income for the system owner through net metering or feed-in tariffs. Grid connection also provides a reliable backup power source and enables the system to draw power from the grid during periods of low solar generation.
2. Off-Grid Systems: In some cases, distributed photovoltaic energy storage systems are designed to operate independently of the grid. These off-grid systems are typically used in remote areas where grid access is limited or unreliable. Off-grid systems rely solely on stored solar energy and may incorporate additional backup power sources, such as diesel generators or wind turbines, to ensure a continuous power supply.
3. Hybrid Systems: There are also hybrid systems that combine the benefits of both grid-connected and off-grid configurations. These systems can operate in conjunction with the grid while also having the capability to function independently when the grid is unavailable. Hybrid systems offer increased resilience and flexibility, providing users with energy independence and the option to utilize grid services when necessary.

In recent years, advances in energy storage technology have led to the development of more sophisticated and versatile photovoltaic energy storage systems that can adapt to various grid configurations and user requirements. As the demand for renewable energy and energy storage continues to grow, the integration of distributed photovoltaic energy storage systems into both grid-connected and off-grid applications is expected to increase, contributing to a more resilient and sustainable energy infrastructure.