I like this way of thinking! As an owner of two solar systems, one installed in 2004 and a second one installed by the author of this topic (which is working wonderfully -- Hi Mark!), I'm in complete support of the premise of PV for EVs. I think the raw numbers here are a bit optimistic, however. What makes it extremely complex is the TOU (time-of-use) rates combined with the tiered billing rates, which vary depending on where you live in California.
x 3 multiplier for solar produced power with PGE time-of-use billing
5,250 kwh’s available from PGE for charging at night for 1,750 kwh’s made during day"
The 3x multiplier is probably a bit overly-optimistic. The higher rate only applies from 1pm-7pm weekdays for the currently-available TOU rate schedule, and only during the "summer" (which actually runs 6 months). So in the morning and on weekends, you're only getting a one-for-one rate on the produced kilowatt-hours. So maybe 60-65% of your solar generation would happen at the higher rates, even taking into account that summer mornings are more likely to be foggy than the afternoons
. The other thing to look out for is if you use a lot of power during the high-rate TOU hours, that may erode the benefit of TOU, since you would have been paying a much lower rate with no TOU and no solar, provided you stayed within the first two price tiers for each month.
Oddly enough, the 3x may in fact fully apply during the winter, but not because of TOU, but rather because of the tiered rates. If you're in the third tier during the winter (whether you have an EV or not), much or all of your winter solar production may effectively offset somthing close to 30c/kWh. But then, the "winter" 6 months of production may only account for about 1/4th (or 1/3rd at most) of your annual production, because of poor sun angle and coudy/rainy skies.
The math is complicated enough that I don't know if I'll ever know exactly how much my solar panels offset my car usage, in dollars (kWh are a lot easier to calculate, and perhaps in some sense, more important!). My best current guess is that I needed the additional ~2kW system to offset somewhere between 15 and 20K miles of driving efficient EVs (Leaf and Fit EV). Part of this is the reasons above, part of it is that I do have some minor shading from tall neighbor trees at certain times of the day. Maybe I'll know for sure next August at my next true-up! In any case, none of this changes my firm belief that at least in CA with PGE's odd tiering structure, PV solar is definitely the way to go to power an EV, provided you have a decent place to install it.
2011 SL-e, silver, VIN 8198, delivered 11 Sep 2011. 37k miles, ~200 GIDs, 9 bars (1st bar lost 3 April 2014 @20,700 mi, 3rd bar lost Aug 2017)
2015 e-Golf SEL
2013 Fit EV, VIN 151, delivered 17 Nov 2012, lease return Nov 2015 at 30k miles
7.7kW solar PV