Many customers ask us about battery sizes and how much storage is right for them. The key is to determine how much energy you are consuming when the sun isn’t shining. That will tell you how much battery capacity you need, which will in turn determine how much excess solar production you require in order to charge the battery. Keep in mind the differences between summer and winter. Many people’s peak energy usage is in winter … just when their solar production is at its annual low point. It will be difficult to perfect the system so that you are fully charging and discharging the battery every day (the key to making your battery economic) and still minimise the amount of extra solar you feed back to the grid. You will have to accept some ‘wastage’ or ‘sub optimal’ economics in your system design. In our opinion, you should perfect the battery sizing, even if it means you feed more solar back into the grid than you would like in summer.