For general interest
The old analogue electric power meters happily spun forwards or backwards to read power consumed or power fed back into the supply. The supply authorities are now replacing them with digital meters that are programmed NOT to register negative power. Power fed back into the supply will be happily accepted by the supply authority but will not reduce the meter reading.
Not sure why they are programmed this way but the effect with many Solar PV tariffs is to substantially reduce the claimed saving in the nett electricity bill. Power that is registered outside daylight hours cannot be reduced or cancelled by daylight solar energy.