Calculating EV emissions
I was considering buying an electric car (EV), but couldn’t find any site on the Internet to tell me what the total CO2 emissions were for these vehicles.
So, as an engineer, I did it myself. For diesel you divide the MPG into 7459. (For petrol this is 6588).
This gives the grams of CO2 emitted per Kilometre. For the EV it is more complicated and very variable. Here you double the actual Grid CO2 emission figure at the time of charge and divide by the miles (or Kilometres) per KWh achieved on this full charge.
This gives the grams of CO2 emitted per Mile (or Kilometre). A 35 Kwh battery achieving 150 miles on full charge is 4.28 miles per Kwh or 6.89 Kilometre per Kwh. You can Google or otherwise ‘Grid Emissions’ for the monthly average current value which is usually around 430 grams per Kilowatt hour; but can exceed 600 g/Kwh at the actual time of charge. (This means a ‘real time’ search; and denied lesser mortals without a deep pocket.)
My own conclusion is that EVs generally produce more CO2 emissions than their diesel equivalent and would often exceed the emissions of my Mercedes 250 diesel in mid-winter. Honestly - Is there something wrong here? Are we not being misinformed?
So, as an engineer, I did it myself. For diesel you divide the MPG into 7459. (For petrol this is 6588).
This gives the grams of CO2 emitted per Kilometre. For the EV it is more complicated and very variable. Here you double the actual Grid CO2 emission figure at the time of charge and divide by the miles (or Kilometres) per KWh achieved on this full charge.
This gives the grams of CO2 emitted per Mile (or Kilometre). A 35 Kwh battery achieving 150 miles on full charge is 4.28 miles per Kwh or 6.89 Kilometre per Kwh. You can Google or otherwise ‘Grid Emissions’ for the monthly average current value which is usually around 430 grams per Kilowatt hour; but can exceed 600 g/Kwh at the actual time of charge. (This means a ‘real time’ search; and denied lesser mortals without a deep pocket.)
My own conclusion is that EVs generally produce more CO2 emissions than their diesel equivalent and would often exceed the emissions of my Mercedes 250 diesel in mid-winter. Honestly - Is there something wrong here? Are we not being misinformed?
Asked on 29 August 2011 by AF, Watlington
Answered by
Honest John
Very many thanks for those figures and for your sensible, detailed argument. I could not agree more. The argument for EVs is lack of tailpipe emissions. But to calculate overall emissions you first have to check how the electricity is produced, and in the UK in daytime most of it comes from fossil fired power stations. Usually, major political initiatives in the automotive field are designed to make money for someone. But I can't work out quite who benefits from the EC demand to cut average vehicle emissions to less than 100g/km by 2020.
Tags:
co2 emissions
electric cars
If you cover no more than 100 miles per day and have easy access to a charging point at home or work, then an EV is ideal for you.
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