I was unable to drive my LEAF as much I would have liked to because I live in a condo-apartment and I was refused to install a charging station or power outlet at my assigned parking spot (at my own expense). I depended on public charging which was no existent in my area and scarce in nearby areas.
My LEAF ended up sitting in parking for months without being charged or driven for six years. The solar spoiler was a HUGE help because it kept my 12 volt battery in perfect condition throughout the year. Even in winter when there was no direct sunlight, just the daylight was enough to keep it charged up.
Even when I started my LEAF after five months (parked in October, started in April), it started right up and the 12 battery was topped up, as if I was driving and charging the LEAF everyday. I wish all automakers add such a solar panel in all cars. It is such a great thing to have especially when cars are not being used as now during Chinavirus lockdown all over the world. I personally know three other families who's cars did not start recently after leaving them unused for a week or two. They all had to get their 12 volt batteries replaced.
There is only one problem with the design of LEAF's solar spoiler. It faces almost directly up to the sky. It would be more efficient if it was embedded in the dashboard or front windshield facing the sky in a 45° angle. Then during the winter LEAF can be parked facing as close to South as possible to maximize charging. As is this solar spoiler is great in only tropical regions throughout the year but not in North America in my experience. During the last few winters my LEAF's 12 volt battery had become weak and the solar spoiler couldn't keep up with the constant slow drain of LEAF's telematics.
Another problem is that the Plexiglas cover on the spoiler fades overtime making it slightly opaque and reducing the solar panel's efficiency. It had unnecessary square shaped designs on the Plexiglas for a modern appearance but they reduced efficiency and aided in UV fading. I tried to polish it numerous times using different methods and compounds but it didn't help.