A Stirling-electric hybrid , Kamen tells me , can travel farther and more efficiently than conventional electric cars ; it generates enough power to run energy-hungry devices such as heaters and defrosters that are essential for drivers who , unlike those he calls the ' tofu heads ' of California , must cope with a cold climate ; and even using petrol , the engine runs far cleaner than petrol-electric hybrids such as Toyota 's Prius .