According to a study conducted by the American Council for an Energy Efficient Economy, the following twelve vehicles are the "greenest" cars currently on the nation's roads.

- The Honda Civic GX, priced at $25,340, runs on clean-burning natural gas. It returns energy efficiency equal to 36 miles per gallon highway, and 24 city.

- The Toyota Prius, at $28,070, gets 48 mpg highway, 51 city.

- The Honda Civic Hybrid is one of the most popular hybrids currently for sale. With an MSRP of $23,800, fuel economy is 45/40.

- The SmartForTwo ranges from $11,990 to $20,990. The vehicle, which is not just small, but tiny, is powered by a 1-liter, 3 cylinder engine getting 41/33.

- At $19,800 to $21,300, the Honda Insight is the fifth greenest car with fuel economy of 43/40.

- Both the Ford Fusion Hybrid and its sibling, the Milan, have mileage of 36/41 at a price of $27, 950 to $28,180.

- The Toyota Yaris, a subcompact, is now the smallest and least expensive vehicle Toyota sells in the United States at $12,605 to $13,365. It's fuel economy is rated at 36/29.

- At $26,780, the Nissan Altima Hybrid gets 33 mpg on the highway and 35 in town.

- The Mini Cooper is available in both regular and extended lengths (the Clubman). Widely known as a fun drive, priced at $18,800 to $24,250, expect 37/28.

- Equipped with a 2.2-liter four cylinder, the Chevrolet Cobalt XFE compact gets 37/25 at an MSRP of $14,990 to $24,535.

- The Hyundai Accent Blue compact, at just $9,970, is the least expensive model on the list of green cars, returning 36 mpg on the highway and 27 in town.

- The 12th greenest car in America is the tiny Honda Fit at $14,900 to $16,410 with fuel economy of 33/27.