It actually mostly just stays in your local area. You are effectively providing power to your neighbors. Some neighborhoods providing too much excess power back

It actually mostly just stays in your local area. You are effectively providing power to your neighbors. Some neighborhoods providing too much excess power back to the grid with solar panels is actually a challenge for grid operators currently. They simply don't have enough cable capacity. So, having a lot of batteries in the area helps them on that front because the power can be dumped there and then extracted when they actually need it.