In the short-term, this also allows homeowners to take advantage of variable-rate billing from power companies. Charging a bank of batteries in off-peak would b

In the short-term, this also allows homeowners to take advantage of variable-rate billing from power companies. Charging a bank of batteries in off-peak would be much cheaper than getting full current during the peak. One problem is that eventually the cost savings is eroded by everyone jumping on the bandwagon to use the off-peak hours, which eventually become more expensive. Also, regarding your point about grid stability, if enough power consumers use these kinds of batteries, some sort of scheduling might be necessary to actually level out the grid's demand across all 24 hours.