Editor's Note: "The Energy Debates" is a LiveScience series about the pros, cons, policy debates, myths and facts related to various alternative energy ideas. We invite you to join the debate by commenting directly on each article. The Facts Electric cars run off batteries and electric motors. None have been commercially available from the major auto companies for roughly a decade, but thousands remain on the road. Meantime, in warmer climates, electric golf carts are frequently converted to be road legal in towns with low speed limits where these low-power "neighborhood electric vehicles" can be operated safely. Cars that run purely off electric power are roughly four times as efficient as ones based on gasoline alone and twice as efficient as hybrid vehicles, said Spencer Quong, senior vehicles analyst for the Union of Concerned Scientists, a science advocacy group. Pros Electric vehicles naturally produce no tailpipe emissions , cutting down on air pollutants that lead to smog and acid rain, as well as carbon dioxide, the major global warming gas. Also, electric cars are extraordinarily cheap to operate. Recharging one costs just a few cents per mile of driving. In comparison, a driver would pay 12 cents per mile for gasoline in a vehicle that gets 25 mpg when gasoline sells for $3 per gallon, according to the U.S. Department of Energy. Now, the rise and uncertainty in fuel prices over the past few years has renewed attention from the industry. "There's also the convenience of not having to go to the gas station — you recharge your car at home, so it's full every day," Quong said. Electric vehicles are also quieter than regular cars, Quong added. Moreover, their electric motors give full torque when they accelerate, without the delayed revving-up that happens when you step on the gas pedal with a gasoline engine. Cons The greatest challenge remains the vehicles’ battery packs. The problem involves getting the cost down and improving the packs’ durability to ensure the cars operate safely and well under all driving conditions — for instance, making sure they perform in the cold and preventing them from catching on fire if they overheat. This also includes seeing how many miles a battery pack can work for. "The newest candidates include lithium battery technology, similar to what you have in laptops, although they still need work," Quong said. Another major concern is what the range of the cars is before they need recharging. "The nickel metal hydride batteries of the electric vehicles of the '90s only had a 100-mile range," Quong said. "Still, do we need an electric vehicle that has a 300-mile range? About half of all people drive 30 miles or less per day." Still, if you do get stuck at work with a low battery, the lack of outlets in the parking lot would prove frustrating. While electric cars do not themselves emit pollutants, most of the power plants that supply their electricity do. Fossil fuels provide nearly two-thirds of the electricity generated in the United States, according to the Department of Energy. Still, consuming fuel at power plants to recharge electric cars is a more efficient process than burning it in a gasoline car engine, Quong said. Moreover, if the electric grid becomes more environmentally friendly by adding on wind, solar and other renewable forms of power, so too do electric vehicles grow even greener. What do you think?