[Flat Six]

Time-Of-Use (TOU) rates are designed to influence when ratepayers consume electricity -- generally to incentivize use during nights and weekends, the off-peak hours.

If your utility provides it (we did at Portland General Electric when I was there ~6 years ago), you can download your electric usage down to the 15-minute increment. Dump it into Excel and it will give you a more granular picture of when (time of day) you're using more/less electricity. Combined with a line meter on your major appliances, you'll be able to identify which ones you can shift to using during off-peak rates (e.g., dishwasher, laundry -- especially w/electric dryer) and how to best program your HVAC to minimize on-peak rates. I'm sure you took advantage of your utility's programs re: mini-splits; if you haven't already you might want to look into any rebates on programmable t-stats.

Using residential storage to try to arbitrage off-peak vs. on-peak rates will likely not pencil out (or not be worth the hassle) compared to making EE improvements & modifying your electricity use patterns to take advantage of TOU rates.