>Hybrid cars work mainly by recovering energy from braking or going downhill to charge the batteries. I always thought that hybrids were more efficient because

>Hybrid cars work mainly by recovering energy from braking or going downhill to charge the batteries. I always thought that hybrids were more efficient because you can size the engine to the average power requirement, and not the peak requirement, thereby operating in a more efficient region most of the time, using the battery reserves for when you need peak power. And for some reason I was thinking that operating an engine at a fixed speed allowed for better engineering trade-offs.