Sunday, March 06, 2011

Electric car not worth the price

One of my Green ICT students saw a Mitsubishi i-MiEV at the Royal Canberra Show. In 2009 I had a brief test drive of the Mitsubishi i MiEV electric car. It worked okay and would be fine for city driving. But I ended up buying an Indian made Suzuki Alto with a 1 Litre petrol engine. So I did a quick back of the envelope calculation to show the students how to work on the relative greenhouse gas emissions of the two vehicles. This shows that replacing my petrol car with an electric one will increase carbon emissions by about 6 tonnes per year.

The iMiEV has a 16 kWh battery pack and a 100 mile (160 km) range. Assuming that it is charged in Canberra with electricity from a coal fired power station, using a conversion factor of 0.90 kgCO2e/kWh for the ACT, a charge will result in:

16 x 0.90 = 14.4 kg CO2e

The Alto produces 0.113 kgCO2e/km and so over 160 km will produce:

0.113 x 160 = 18.1 kgCO2e

So replacing an Alto with an iMiEV will save about 20% of the kilograms of carbon dioxide equivalent emissions. But the iMiEV costs about three times as much as the Alto.

Note that this does not allow for the possibility of running either of them on renewable energy (the MiEV on solar power and the Alto on bio-fuel).

A solar panel rated at 0.085 kW will produce on average 0.41 kWh a day in Canberra, or:

0.085 / 0.41 = 0.21 kW of panels per kWhr per day

Assuming I drove 20 km a day, I would need:

16 /8 = 2 kWhr per day

So to provide this much power, on average I would need:

2 * 0.21 = 0.42 kW of solar panels

A system this size would cost about $2,000.

The extra few thousand dollars to run the electric car on solar power does not sound like a large investment. But keep in mind that I could buy the petrol powered car and use the money saved to but more solar panels to run my house, resulting in a much larger reduction in greenhouse gas emissions.

Assuming an Alto costs $13,000 to buy and $15,000 for fuel and servicing over ten years, that is $28,000. Assume the iMeEV is $39,000 and requires no servicing, and I buy a $2,000 solar system to charge it, the total cost is $41,000. I would save $13,000 by buying the Alto. This could buy about a 5 kW solar system, producing 14,000 kWhr a year, saving about 8,000 kg CO2e per year. The Alto will cause 1,653 kg CO2e per year. So overall that is about 6,000 kg CO2e per year less than with the MiEV.

The cost of electric cars will likely decrease over time. However, the cost of solar panels will also reduce over time. As a result it may be cost effective to use electric cars for the foreseeable future.

Note I did not take into account the energy needed to make the two vehicles. The MiEV is likely to take more energy to produce as the Lithium batteries used take considerable processing to make.


Department of Climate Change and Energy Efficiency 2010, National Greenhouse Accounts (NGA) Factors, July 2010,>

National Transport Commission 2009, Carbon Emissions from New Vehicles,>

Steven, JE 2010, 'Review: 2010 Mitsubishi i-MiEV', AotoBlog, 2010,

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