Using batteries to offset peak rates

All the consumer grid batteries and many of the commercial versions tout their ability to save money by charging at night when electricity rates are low and discharge during the day to avoid using grid electricity when the rates are high. And this makes sense.

But we need to be careful. If the grid is ever maintained in such a way to make it more robust, or if there become enough grid battery installations, then this price disparity between night and day will be lessened. And consequently, using this disparity in price between night and day to pay off the battery installation would take longer.

There is no doubt that grid batteries are a good idea. If nothing else, when solar and wind power become cheap enough to compete with coal and nuclear we'll need a battery to make them useful. And even if the disparity between night and day is lessened, with an inexpensive enough battery even a longer pay-off time will still make financial sense.

There are also people that say rate-shifting is a regulation problem and not an engineering problem. And if that's true it means that rate shifting could become fiscally unviable at the stroke of a pen. And this is true to some extent. But even if the regulations could change overnight, a lot more would have to change before it was politically possible. And it would not make grid batteries a bad idea in the context of renewable energy or simply as peace of mind that comes with a battery backup.