Basically, yes. Recall that in California the cheapest production is actually mid-day now, since that's when solar produces most strongly. There's a chart here

Basically, yes. Recall that in California the cheapest production is actually mid-day now, since that's when solar produces most strongly. There's a chart here that shows renewable production over the course of the day and includes battery charging/discharging in another chart at the bottom: http://www.caiso.com/TodaysOutlook/Pages/supply.aspx http://www.caiso.com/TodaysOutlook/Pages/supply.aspx Looking at November 8, 2018 you can see that batteries began charging around 7:30 AM as solar power started ramping up for the day, and switched over to discharging around 4:00 PM. There were also brief excursions to discharging from charging in between to deal with smaller fluctuations. If you compare that supply chart to the net demand chart for the same time, you can see why the batteries are mostly charging in that time period: http://www.caiso.com/TodaysOutlook/Pages/default.aspx http://www.caiso.com/TodaysOutlook/Pages/default.aspx There's a big "scoop" taken out of net demand by solar in the middle of the day. After the early-evening demand peak there's often a smaller "scoop" taken out by late night wind power. In states with better wind resources, like Texas, the net demand reduction is usually in the middle of the night instead of the middle of the day. http://www.ercot.com/content/cdr/html/CURRENT_DAYCOP_HSL.html http://www.ercot.com/content/cdr/html/CURRENT_DAYCOP_HSL.htm... Today's wind generation in Texas is up past 12,000 MW as of 11:00 PM but dropped as low as 2,000 MW at noon.