In the case of a well-designed PV system, a large amount of energy is exported back to the grid. This is because the system is generating more energy than a property is using at that particular time. For instance, if you’re out of the house on a sunny day, your home probably won’t be using all of the energy your system generates and so energy will be exported straight back to the grid.
At other times in the evenings you’ll be buying energy back from the grid because your system isn’t generating at that time. So, sometimes you’re producing more energy than you’re using and at other times you’re not producing enough - there’s a mismatch in supply and demand!
This can be very frustrating especially from April to November, when your PV system is working at its best and probably producing enough energy overall to cover the majority of your home’s energy demand.
This is the problem that a battery helps to solve. It can store the solar energy that’s generated but not used at the time, so you can use it later on when your system isn’t generating.