Electroman: Those tables raise a lot of questions, don't they?
* Seems like there's an error in the 2nd table? I get an average monthly cost of $182,
* Do you really use as much or more power at night than you do during the day? That seems strange to me. I use an average of 47kWh/day and around 70-80% of that is during the day That includes charging our Model 3 as and when required. Granted we're retired and so tend to be home more than a young working family, but yours still seems a strange distribution to me. Are you sure you're being billed correctly? You may want to put a time-base monitor on your panel for a few weeks.
* Assuming you don't mind occasionally paying for grid-supplied power on days when you exceed your average (which from your table will be quite a few especially during the summer months) and want to just base your PW requirements on the average, and assuming a 100% efficiency (charge/discharge) from your PW (impossible - you'll probably be around 85-90% when new) you'd need 2 PW. If you take efficiency into account, you'll need 3 to meet your 26kWh estimate. Of course that would reduce the number of days that you have to draw from the grid to very few.
* The big question, I think, is whether your grid supplier will allow you to brokerage the power. I don't know of any residential suppliers that will allow home brokering (purchasing power during a low rate, storing it, using it during high rate period). Since your supplier will have to approve your installation and provide you a PTO, they will insist on a control system that prevents charging your batteries from the grid except after a power outage that occurred during the high rate period.
* If you use the batteries every day the expected battery life will be pretty low (a couple of years?). These batteries are not designed for daily (brokerage) use but for "emergency" backup. I think Tesla's PowerWall is the best out there available for residential use but not even Tesla PW is intended to be used every day through a full cycle.
Of course if you already have solar PV and your plan is to use solar to charge the batteries then the brokerage question goes away.
I'd be interested in hearing what your grid supplier has to say about your plan. Also if you have any research on PW life expectancy when fully cycled every day of the year.