This kit develops 30 watts, that's about 0.04 horsepower (when the sun shines). Since we use several horsepower on average while driving, I don't think this kit would provide much help. Maybe the reason for their good MPG numbers is they are in Nevada (desert, flat) and they are going slow. For 30 watts to make a 10% difference would mean that we, on average only use 0.4 horsepower (that would run a bike at 20 miles per hour on the flat).

JeffD