Sunday, August 23, 2009

Is the Electric Smart so smart or not so smart?

Larry and avid follower of the Green Machine asked me to opine on whether the conversion of the Smart for Two into an electric vehicle is a smart or not so smart idea. Daimler has taken an equity position in Tesla Motors and Tesla will provide the electric propulsion systems for the Smart. Smart is also an affiliate of Daimler and hence the connection of Tesla to Smart and visa versa.

The standard gasoline Smart for two has an empty mass of some 1,653 pounds. With two people in it, the mass would equal a ton. The Tesla roadster has a mass of 2,723 pounds and with two passengers it would have a mass 3,170 pounds. The Smart has a mass equal to 63.1% of the Tesla before it is fitted with batteries and a motor and the internal combustion engine and gas tank are removed. Mercedes has stated they will fit the electric Smart with 14 kilowatt hours of lithium ion batteries. With current state of the art power densities this will add some 300 pounds of batteries to the vehicle. With the swop out of the internal combustion engine and gasoline tank for an electric motor, I estimate the electric Smart for two will have an extra 150 pounds of mass over its gasoline counterpart. The electric Smart for two will have a mass approaching two thirds that of the Tesla. Ignoring aerodynamics for slow city driving the Smart for two will go one and a half times the distance of the Tesla on the same amount of charge.

Smart is being smart by only equipping their car with 14 kilowatt hours of battery storage versus 54 kilowatt hours for the Tesla. This will still add some $15,000 to the cost of the Smart. This means the electric smart will retail in the low $30,000s. Their will be some greens who will fork out this amount of green for a car with a range of seventy miles and that has a top speed of 62 mph. Interestingly Daimler is not claiming 400 mpg for their car. They are making honest claims about range and speed and have also been up front about the added cost of the battery system. I know their claim of range is honest as the 14 kilowatt hour battery should propel the car 70 miles in city driving with about 20% of the charge to spare as one does not want to fully discharge the system.

What if Smart wanted its car to have the same range as the Tesla? After doing a Newton Raphson interpolation of the net added mass for the Smart to have a range of some 240 city miles, I come up with the need to add 750 pounds to the Smart such that it will now have a mass of 2,750 pound with two passengers. This is getting quite heavy and makes no practical sense.

For the simple city driving, the Electric smart will need 0.2 kilowatt hours of electricity from the grid to travel a mile. The same car equipped with a gasoline engine and traveling in the city will get 40 mpg. The CO2 per mile traveled under these ideal conditions will be 0.5 pounds of CO2 per mile for the gasoline version and 0.26 pounds of CO2 per mile for the electric Smart using the average emissions for electric power generated in the USA. The electric Smart is a smart alternative for reducing CO2 emissions. The problem is one of cost and the question remains whether society can afford to double the cost of a car to halve the CO2 emissions?


  1. Paul a retired prof from Stanfors sent me this question to my email so I have posted it

    If the electric Smart car saves 0.24 pounds of CO2 per mile and if we assume
    about 5000 miles for about the city driving per year, we are talking about
    saving 1200 pounds of CO2 and $375 for gas per year for an extra initial
    cost of $15,000. If we assume an interest cost of 7%, this amounts to $1,050
    per year additional cost. It sure does not seem to make economic sense to
    me. I think it would be helpful to show the dollar costs per year on your




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