I would never expect a car company to sell a solution that looks like this, but integrated into the vehicles body you can remove all the drawbacks but weight (and optimize weight a lot more than the DIY solution can). See what Aptera is doing...
But then you have to charge your car. The win here is convenience. If you average more charge per day than you average driving (and you have a large enough battery to load balance) you practically never have to charge (ignoring outliers like long road trips).
It's 2kW.
Tesla are 2 tons monsters that charge at 100 000 Watts. 100 Watts produced by integrated panels like this, are most likely not even enough to power up battery controller!
If you charge Tesla from normal house plug in cold, 2KW are not enough to heat up battery pack. So car has to use energy from batteries for heating! So "charging" will actually reduce energy!
Small solar panels are great for fixing parasitic battery drain on vehicles though!