I'm on a "time of day" billing rate for electricity. California has lots of solar so rates are low during the day but go up significantly at about 4pm when solar starts to taper off. I have solar and feed power back to the grid during the low rate time of day. I considered getting some of those batteries and charging them at the low rates and then feeding the power back to the grid after 4pm where I'd get the maximum credit for the power.

Haven't done it yet but it might be worth it. I think the power company would appreciate it because they need the power at that time.

Mike