By Scott Hamilton

I have been studying electric vehicles (EVs), hybrid electric vehicles (HEVs) and internal combustion engine vehicles (ICEs) for just around a decade, and up until this week thought that HEVs were likely to be the best choice for improving fuel economy and reducing environmental impacts. However, after reading a very interesting article on by Selin Oğuz last week, I have changed my mind. You see, I was making the same mistake that most scientists involved in these studies tend to make. We were ignoring a couple of factors in our calculations.

Oğuz covers something unique, the Life Cycle Emissions of various vehicles. In her report she gives detailed averages of all emissions related to EVs, HEVs and ICEs during three phases of their life cycle. First, she covers the production emissions. These are ignored by most of the people studying the topic under the incorrect assumption that the manufacturing environmental impacts are the same. I am guilty of the same assumptions. As it turns out, the manufacturing of EVs and HEVs are only slightly less impactful than ICEs, but when you consider the batteries, HEVs are exactly the same and EVs have a 40 percent higher rate of production emissions.

The second phase of the life cycle is the Use-Phase. This is the area of focus for most who study the topic and there are two stages during the use of a vehicle where emissions are produced, and we are often guilty of ignoring the first stage. This is the stage of Fuel production. Since both HEVs and ICEs utilize internal combustion engines, they both use fossil fuels and the production of their fuel causes emissions between 12-14 tCO2e, to be exact. A tCO2e is a unit of measurement utilized in the industry to indicate the tonnes of carbon dioxide equivalent emitted by the process. It is at this stage that EVs are the biggest losers, just like the manufacturing stage. Their emissions levels during electricity production comes in at 26 tCO2e (112 percent higher) than that of HEVs and ICEs.

At this stage things start to look bad for EVs and their likelihood to save the environment. However, the direct emissions from the vehicle (i.e. the exhaust) is zero for EVs, 24 tCO2e for HEVs and 32 tCO2e for ICEs. The final stage is nearly a tie at the end of the vehicle’s life; the recycling of components offsets a small amount of the carbon emissions and EVs are granted more carbon credits during the process, as they have more recyclable components, which results in a slight difference overall. The Oğuz report shows, over the life of the vehicle, 39 for Evs, 47 for HEVs, and 55 for ICEs.

There is one factor Oğuz fails to cover in her report that, for me, makes ICEs the clear winner. She fails to consider the useable lifetime of the various vehicles. EVs last between 100,000 and 200,000 miles, with a battery replacement around 100,000 miles. HEVs last at most 100,000 miles and gasoline cars average 150,000 miles. When you consider the battery replacement will increase the emissions by another 5 tCO2e, the new EV total is 44 tCO2 making it nearly equivalent to the HEVs, and given the higher mileage life expectancy of ICEs, they average out at less emissions per mile than the alternatives. This means ICEs are still the best vehicles for the environment.

Until next week, stay safe and learn something new.

Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to or through his website at

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