Off-grid System
This is a system that is not connected to the national electricity grid (mains power) and uses batteries for storage. This system is often used in circumstances where the grid is difficult and expensive to access such as in a remote area or where it is impossible to connect to the grid such as on an island. An off-grid system can sometimes be cheaper than extending existing power lines.
The way it works is that when the generator (wind turbine, solar PV panels, hydro etc.) is producing electricity the household can use this electricity immediately. If the turbine is producing more electricity than is required by the household at that particular moment any unwanted excess electricity is stored in the batteries. When the turbine is not producing enough electricity to satisfy the household any electricity needed is taken from the batteries. Off-grid systems can be economical compared to the cost of electricity generated by using a diesel generator only.