I think it's even more than that. The hybrid engine has to run one single RPM to drive a generator, it can be vibration insulated, probably needs to be only sma

I think it's even more than that. The hybrid engine has to run one single RPM to drive a generator, it can be vibration insulated, probably needs to be only smaller because it doesn't have to provide the high max power the conventional motors have etc. It's why I believe hybrid cars that use a gas motor only to charge the batteries are more reliable and more efficient.