In theory he can do daily driving on electricity from solar panels, saving the gasoline for emergencies when he needs to drive long distances. Unfortunately there are two problems with this.
- The amount of solar panels you can put on a car can only generate enough energy to move an EV or PHEV about 5 miles per day. Granted, you can leave the car parked several days and only drive it once in a while. Or bring a huge bank of extra solar panels and plug it in. But the mobility from only rooftop solar panels is pretty restrictive.
- Gasoline degrades over time. Unless you've added stabilizers, after about a year it's pretty much won't run an engine anymore (its combustion characteristics have changed too much). A lot of zombie apocalypse shows make this mistake too. Technically you can keep it indefinitely if you isolate it from the air. But because of how much it vaporizes with changes in temperature, nearly all fuel tanks and fuel cans have a vent hole to equalize pressure. So unless you've stocked up on stabilizers beforehand, you're only looking at about a year of usability. Diesel is a better option. It's more like vegetable oil and can last 5+ years (unless algae starts growing in it).
The best thing about a hybrid in our world is that it lets you avoid running the ICE motor in inefficient states (e.g. starting from a dead stop). The peak efficiency band of an electric motor is much broader than an ICE motor. So you can use the electric motor to move the car in situations where the ICE would burn a lot of fuel for little effect. Combined with regenerative braking (though that only recovers about 30%-35% of the energy), that's why hybrids get much better mileage ratings than a pure ICE. Starting from a dead stop is especially brutal for ICE motors.
