My point also was not that the numbers are dependent upon 2 T105s but to make the calculation easier to follow. It should be scalable to any size battery bank.
I agree that I have not fine tuned the analysis to account for charging and inverter inefficiencies, but I am rather taken aback at how much SCE would be charging me for TOU during peak times as well as how little they charge at below baseline at night, effectively 1 cent per kWh.
Initially my goal was to show that if one cherry picks the highest rates with a small system, that the batteries could be more than paid for by the difference. Now I am not sure if that is the extent of it. It may be that more of a system could at least break even depending on the load with the desired benefit of also ending up with a UPS of sorts for a good portion of a residence, paid for by the difference in TOU rates. After all, the delta is '46 cents - battery cost' up to the baseline.
A simple system might be:
Timer -> Charger -> Battery Bank -> Inverter -> transfer switch - > electrical panel
where the timer only runs the Charger at the time period of the lowest rate.
I will probably look at more specifics in either my home or cabin to see if it really makes sense for me to consider this at all.
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Found Trojan T-105-RE on sale in San Diego for $125. That calculates to 11.57 cents / kWh. It is of interest that even Industrial does not have as good a price ratio (eg IND17-6V @ 17 cents / kWh)
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$$$
Added Cost for Inverter and Charger (prorated them for 10 years - $744) so that now the cost per kWh is 12.44 cents. This is based on a sale price if T-106-RE at $125
$$$
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My baseline is 13.8 kWh which for TOU would allow charging for 10 hours at 1 cent / kWh. This brings the cost of battery-produced power to 13.44 cents / kWh
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My tier 1 is 14.496 kWh. This gives me a surplus of about 1 cent / kWh.
My conclusion is that the risk of premature failure of batteries or electronics outweighs any slight cost benefit and does not compensate for the labor of battery maintenance.
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