Solar PV systems generate energy during the day, powering your appliances at the point of demand. However, when production exceeds the load demand, this energy is exported to the grid – meaning that on average, as little as 25% of the free energy generated is used within the home.
By adding batteries to a solar PV system, this surplus energy can be stored and used when it is needed – this can be during the day or overnight. This has no implications for the feed-in tariff which is paid based on generation, not export.
There are two possible solutions for domestic storage systems – AC or DC coupled.
AC-coupled systems are recommended as a retrofit solution (for those who have PV installed). There is no impact of FIT revenues for those on a high rate (owing to charge/ discharge efficiency losses) and no need to replace the existing DC inverter. They also open up the possibility of charging batteries from the grid to exploit peak/off-peak price differentials and therefore can be installed without PV. AC-coupled systems can also be used with new PV installations and provide the most flexible solution in terms of siting batteries and for grid-trading purposes.