Instead of always sending spare AC power back to the grid, this system stores spare DC power in batteries and converts it back to AC so you can use it in your property when your panels aren’t working – at night, or when it’s very cloudy, or even if there’s a power outage.
In summer with a correctly designed system your batteries will often be fully charged. Spare power will then go to the grid to be shown as a credit on your bill. In winter it can be cost-effective to top up your batteries overnight if you have an off-peak tariff.
A hybrid system doesn’t give you complete freedom from the grid, but does enable you to use the grid merely as a backup or top-up device, in much the same way that a generator would be used.