One 8,760 line Excel spreadsheet later, I have your answer: On 51 days in calendar 2021, my solar production was less than the sum of my partial and peak consumption. So I would not have had enough stored to discharge throughout peak and partial peak periods. We are in sunny (but sometimes coastal overcast) Oakland Calif, so 13% shortfall days is to be expected, 51 out of 356. Over that year, our solar production was 97% of our consumption kWh.
The cost savings is probably less than $100 per year. But since my True-Up is in the $100 vicinity (by design), small improvements result in large percentage changes in the final bill.
To find that 51 day answer, I downloaded the SAM-8760 file, (365 X 24 lines of hourly consumption data) from my Enphase micro inverter system, as well as daily solar production for the year. An afternoon on Micro$oft's support site and a few inglorious kuldges got me a "pivot table" showing the count of 51 days to answer your question. A sunny day with low consumption might leave a high PW state of charge, so the exact kWh saved would need an even more complicated calculation. Hence the SWAG <$100 above.
Folks with less solar and/or higher consumptions (think heat pump winter heating) would see much more savings, of course.
SW
