At steady highway speeds you gain nothing and need to haul extra weight. The weight penalty isn't as bad as you might imagine. On the Toyotas, the hybrid desi

At steady highway speeds you gain nothing and need to haul extra weight. The weight penalty isn't as bad as you might imagine. On the Toyotas, the hybrid design replaces the regular transmission, flywheel, and torque converter (if automatic) or clutch (if manual). So the big weight penalty is mostly the battery pack.