Selectronics inverters use the solar input to charge the battery bank. Once the batteries are fully charged, then the units can export power to the grid (as it is generated). Rather than export at peak times, you just use the battery bank to provide for your own power requirements, allowing you to minimise your time of day peak tariffs - utilise battery power instead of grid power. They also have smart charging functions so that they can utilise low time of day tariffs to charge the batteries from mains etc.