You should probably consider the solar system separate from the car, and calculate the car vs grid rates based on overnight charging.
We don't have a solar setup and the overnight rates in Ontario are pretty low, which is when we charge the car.
I have talked to a couple of solar installers here and for our place, while the aspect is good, the surface area would only be sufficient for about 3.5kW. Most of the installers I've talked to here don't want to bother with less than 5kW. :-/ The payback on the solar system alone would be on the order of 15 years against market rates. We don't plan to be here that long.
From an ROI perspective vs gasoline, I can give you some real world numbers. Over the last 5 1/2 years of driving BEVs we've done over 100,000 km. Given the price of regular gasoline here, at roughly 9L/100km (our old Mazda), our Smart ED has saved us roughly $2,500 per year after subtracting the electricity costs. Our TM3 would be somewhat lower than that rate, but has lots of other benefits. ;->
So just looking at the Smart, the car will be paid off in gasoline savings in about 4 more years. The first "free" car we've ever owned.
The Tesla would take about 3x longer to pay off, but you should probably be looking at the gas savings and the lower maintenance vs an ICE as icing, rather than a payoff. An ICE is always a money pit between the fuel, maintenance, depreciation and other considerations. The environmental benefits are obviously really important, but harder to quantify. The ROI vs a BMW 3 or C class vehicle is however vastly better, but still unlikely to net out to zero. The GHG delta would be paid off in about a year. The financial delta to a similarly priced car is probably already a wash, depending on how you value the feature balance between vehicles.
if you are able to charge the car in the day at home, and drive a lot at night, then the valuation w/ solar is likely to be a slam dunk. But I'd assume that's not the case.
The home storage would simply add to your capital outlay for the car and extend the payback period. Outage security and grid independence aside.
Not sure that was all that helpful. I'd certainly like EV+Solar+Powerwall myself.
