To estimate out how much slack there is in local distribution systems, you want to look at the demand curve rather than the duck curve. Further, you want to loo

To estimate out how much slack there is in local distribution systems, you want to look at the demand curve rather than the duck curve. Further, you want to look at the peak of this curve on a high-demand day -- for California, that means a hot summer day. For northerly regions it will be a cold winter day. http://www.caiso.com/TodaysOutlook/Pages/default.aspx http://www.caiso.com/TodaysOutlook/Pages/default.aspx It looks like the minimum CAISO demand today -- during the shoulder season -- was 19 gigawatts. Here are the CAISO historical peak loads from 1998-2018: https://www.caiso.com/Documents/CaliforniaISOPeakLoadHistory.pdf https://www.caiso.com/Documents/CaliforniaISOPeakLoadHistory... The peak last year was 46 gigawatts on July 25. The peak in 2017 was 50 gigawatts on September 1. So I do think it's fair to say that there is a 2x factor of minimum:maximum use on at least some existing grids. There's one more issue, of course: how much minimum-period slack is left on the day of high demand conditions? Using the date picker on the demand curve to go back to July 25, 2018, it looks like demand bottomed out at 26 gigawatts around 4:00 AM. There is still a significant diurnal variation in demand that could be used for several hours of nighttime EV charging without increasing system capacity.