Solar is a great green technology that would seem to go hand-in-hand with electric vehicles to charge the batteries. In fact they are a great match, but not in the way some people may think.
Solar energy is a great renewable energy resource. Many EV drivers put solar panels on their home to help charge their EV and reduce their long-term power bill, and rightly so. However, putting solar panels directly on an EV actually involves a number of challenges. For a vehicle the size of ours - a full-size truck - trying to charge the main vehicle battery for additional range is basically futile.
The problem comes down to the energy density of solar. Simply put, only so much energy from the sun is available per square meter, and solar panels can only capture a portion of that energy. Further complications arise from the orientation of the panels - the solar panels on a home are aimed to face south (in the northern hemisphere) at the appropriate tilt angle for the latitude, and sometimes adjusted for the season. Some panels can even move and track the sun. On a vehicle, however, we really only have the horizontal surfaces to work with - like the hood and roof - and they are at a very flat angle which is not the most optimal for making power. The bottom of the truck bed isn't ideal either for obvious reasons. And parking in partial shade near a tree may also mean that a certain panel can't make enough power, which can affect the output of the whole array.
With that said, we do believe there can be a role for solar to play on a full-size truck like ours. There are ancillary functions where we feel solar could offer some advantages. These are not our priorities at the moment, but we recognize the opportunity for the future.
One example is climate control, especially in hot climates where the sun is high. Even getting a couple hundred watts from a small solar array may be enough to run fans to provide circulation of air into the cab to avoid the 140° - 160° F peaks that are possible during the summer. By venting the cab, it will make it more comfortable and quicker to cool when you return to the vehicle, and will also reduce the stress and wear on the interior.
Another possible use for on-board solar is for long-term storage, to compensate for parasitic or "vampire" drains on the battery. One example scenario would be when parked at an airport parking lot while away for a few weeks of travel, your state of charge would be able to remain the same without degradation.
Even in a much shorter term, like during the day on a job site, solar may be able to keep the battery at a consistent level while using power tools or chargers powered from the truck's on-board power inverter throughout the day.
For these tasks and more, a smaller set of panels able to make 250 to 500 watts of power would be sufficient. Some extremely lightweight, small and highly efficient vehicles with a solar array covering a large portion of the body or roof may be able to gain some appreciable charge from solar power, but given the size of pickups, their design and power, to fully charge the battery in this manner could take months.