Thanks for the feedback. However, based on most of the responses, not sure if the gist of my question got through clearly. The question is not whether a Prius is a good substitute for a dedicated gennie (of course not). The question is if you're a typical two car family and one is a hybrid and one is a typical gasoline powered vehicle, is using the hybrid for emergency power like that NJ guy did more efficient than using the other car for power? I'm wondering if the hybrid is designed to produce electricity for less fuel per amp-hour than the alternator in a typical gas car?

One big conflicting factor for someone thinking of this choice may be whether you actually need to drive anywhere during the outage. If you do need to drive much, say, to check on friends or family members periodically during some disaster, then the fuel efficiency of the hybrid (compared to whatever other gas vehicle you may have) may tip the balance to using the gas vehicle for power and saving the fuel in the hybrid for driving around.