Hertz is offering hybrid cars at its California locations (I mean, maybe they have them elsewhere too but we found them here in San Jose and we also rented one recently in SF). As we all know, Hertz is not your cheapest car rental company, and sometimes the most expensive one. But their service is hard to beat and we never had any nasty surprise with them. The point is that if you rent a Prius as we did you probably save the difference in $$$ you pay to Hertz and you would pay to discount rentals. Our car was clean, with very low mileage and we had no problem operating it - although there are some differences between our vehicle and a hybrid. You are also advantaged in parking when driving a hybrid vehicle in many Californian cities.