further to the above, which is right, but part of the story.

The way to tell which way the current is flowing.is by looking at the voltage gradient - if the voltage at the transformer  at the street end is higher than the voltage in the house power flows in the direction that the voltage is lost towards the house, and the current is in phase with the voltage. ()

If there is excess power in the house then the voltage at the house end is raised and the voltage drop, and the phase of the current, is reversed. It is the phase relation ship between voltage and current that determines if the meter goes backwards or forwards, and the voltage drop or rise (and street cable resistance) that determines how much current flows in a given 'direction'. (*)

In a traditional network, the voltage starts high (near 250V) at the transformer, and falls towards the far end off the village. If the houses are generating this is reversed, and indeed solar panel inverters must be set to trip out if the voltage rise is too much;  to  protect other users of the network.

It is the same with the batteries in parallel thing - the current flows out of the full one with the higher voltage, and into the flatter one with the lower voltage.

Mike

(here by current flow direction, as really mains is AC and reverse every cycle, we use "in" and "out" to mean "in time with" our "in antiphase to", the alternating voltage relative to the direction of interest.)

further to the above, which is right, but part of the story.

The way to tell which way the current is flowing.is by looking at the voltage gradient - if the voltage at the transformer  at the street end is higher than the voltage in the house power flows in the direction that the voltage is lost towards the house, and the current is in phase with the voltage. ()

If there is excess power in the house then the voltage at the house end is raised and the voltage drop, and the phase of the current, is reversed. It is the phase relation ship between voltage and current that determines if the meter goes backwards or forwards, and the voltage drop or rise (and street cable resistance) that determines how much current flows in a given 'direction'. (*)

In a traditional network, the voltage starts high (near 250V) at the transformer, and falls towards the far end off the village. If the houses are generating this is reversed, and indeed solar panel inverters must be set to trip out if the voltage rise is too much;  to  protect other users of the network.

It is the same with the batteries in parallel thing - the current flows out of the full one with the higher voltage, and into the flatter one with the lower voltage.

Mike

(here by current flow direction, as really mains is AC and reverse every cycle, we use "in" and "out" to mean "in time with" our "in antiphase to", the alternating voltage relative to the direction of interest.)