Further answer - The consensus from people who know this better than you & I, have these cars, and in some cases have tried.. is basically - it won’t charge much, and it’s way more expensive than the electricity it is going to generate.
Note there are AC-DC inverter losses of 10-20%. plus input->battery charge losses which are non-linear and very bad at the low end. For example a Tesla won’t even take a charge if the input is below the ~300-500W range in good weather. In cold weather say Northeast US winter, the floor is closer to a 1kW input as there is a heating system to get the battery put to temperature for charging that is going to eat almost all of that.
https://forums.tesla.com/discussion/93521/solar-panels-on-th...
https://forums.tesla.com/discussion/150998/charge-tesla-w-so...
2) In good weather you are probably looking at post-inverter input to charger at 700W, with charger losses meaning about 400-500W making it to the battery. So that is, in an efficient Tesla about 2 miles of range for every hour of peak sun. Depending on your location, orientation and time of year you might expect peak sun hours of 3-6 hours/day. So grand total 6-18mi/day of range added making a lot of happy assumptions and not moving your car during lunch. This amount of charge per day could be acquired in 1-2 minutes at a supercharger and worth about 30-75cents. Or charge at a L2 charger in your own garage in 12-36 minutes.
(Or, equivalently, multiply the power from the PV by time to get daily energy output).
The “won’t take a charge below 1 kW” is definitely a killer, if it’s a limit of the batteries themselves and not the charging circuit logic.
4m length * 2m width * 1kw/m^2 insolation * 50% loss due to the panel area being calculated by ground area and it not tracking the sun and therefore not getting peak output * 20% cell efficiency = average power 800 W
My BOTE calculation above should use 25% instead of 50% for day-night average of PV panels horizontal to the ground. Can’t edit now, though. 25% is the planet-wide average for day-night and seasonal variation because that’s the ratio of the surface area of the Earth to the area of a disk intersecting the same flux of sunlight at 1AU (4πr^2 : πr^2).
With that correction, that’s 400 watts average over 24 hours (as in: no not merely the peak at noon); which means 24 h * 400 W = 9.6 kWh per day.
If you drive 60 miles per day, and each mile consumes 241 Wh of energy, then you consume 14.41 kWh of energy per day.
Model 3 is about 5m by 2m, and is apparently rated for 241 Wh/mile
4m * 2m * 1kw/m^2 * 50% * 20% = average power 800 W
(50% because the panels are flat, 20% because cell efficiency)
241 Wh/mile * 60 miles/day = average usage 602 W
I’m not sure what fraction of the day people drive for given that I’m not a driver, but I’m eyeballing 5-10%. I acknowledge professional drivers — taxis etc. — can’t possibly rely on PV alone, that PV can only supply a fraction of what they need (my 10% guesstimate), but I still think this should help with the general public. Or are my assumptions way off?