-- Last Updated: Oct-22-12 12:56 AM EST --
First, whether they are "computer vehicles" or not makes no difference. With extra weight and wind resistance, the car will do the same thing it would otherwise do when going uphill. Second, the gas engine will take on as much of the load as it has to if a period of unusually hard work lasts too long for the battery/electric-motor to continue providing assistance (battery power is normally a short-term thing when extra oomph is needed, not full time, so the gas engine is fully capable of doing the work when necessary - there's just less reserve power in that case). The gas engine of a Prius, for example, has much more horsepower than the compact cars made around 1980 and earlier, and I can vouch for the fact that a 50-horsepower car from the 70s or early 80s was more than capable of hauling two canoes plus people and gear. I have it on good authority that before my time, the same was true of 40-horsepower VWs. You won't be winning any drag races with such a rig, but it'll get you where you are going. Low horsepower nowadays doesn't mean your car can't pull whatever practical amount of load you ask it to, it only means it won't have as much reserve power when accelerating up to speed, and it MIGHT have to go slower up really steep hills. No modern car runs at it's horsepower limit simply because there are boats on the roof and a bunch of stuff inside.