What is the most efficient car in the world? Here are some street legal ones: Here, they say: "Boasting NEDC consumption of just 12 kilowatt hours per 100 kilometres and zero carbon dioxide emissions, the smart fortwo electric drive is the most economical and climate-friendly alternative in urban traffic." Here, Tesla EPA sticker says "City: 32kW-hr/100 miles, Hwy: 33 kW-hr/100 miles". Here, Wrightspeed X1 says 200Whr/mile (20kW-hr/100 miles). Here, the 2000 EPA Fuel economy guide listed some EVs like this: NISSAN Altra EV ........... 29/26 TOYOTA RAV4 EV .......... 29/37 FORD Ranger Electric ... 40/45 Here, they listed the EV1 as 30/25 Then there are all the prototypes competing for Auto XPrize. Including the Aptera which supposedly does 120 miles out of 10kWh.