ICE vehicles vs Electric Vehicles: An Analysis of Lifetime Carbon Emissions
Preface: This memo was written for the Stanford course GSBGEN 569: The Open Road taught by Don Wood and Stefan Reichelstein. This memo was co-written in equal parts with Anna-Katharina von Krauland and Brad Mitchell, whom I would like to sincerely thank for their work.
Introduction
Vehicle electrification is one of the biggest trends in the transportation sector and will shape this industry over the coming decades. Transportation is one of the most critical sectors to address in transitioning to a carbon neutral society, as the sector accounts for an estimated 28.5% of all GHG emissions, with over 90% of the fuel being petroleum-based. Massive gains have been made in Electric Vehicle technology, and sales are rising. Despite their benefits opposition remains on the grounds that EVs are actually not CO2 negative since electricity itself is not typically CO2 free. Our goal is to examine this claim across a variety of grids and fuel types.
Methodology
We have analyzed these claims using the VW Golf in its gasoline, diesel, and electric variants. CO2 emissions for each model have been assessed based on the following grids: The states of California and Wyoming, Germany and a hypothetical carbon-free grid. We have selected such geographic areas to represent extreme regions, which we expect to inform the upper and lower bounds of EV benefits. The approach incorporates assumptions that consider full-life cycle effects of EVs versus their ICE counterparts.
Note that our analysis specifically does not consider items such as: range, locations of specific manufacturing facilities, CO2 effects of differing maintenance requirements (i.e. more frequently replaced tires from additional EV weight), or longevity/recycling. We have deliberately focused on the core contributors of emissions for purposes of this project.
Why VW Golf?
We have chosen the VW Golf for three reasons:
1) It is sold worldwide in relatively standardized variants,
2) It exists in gas, diesel, and electric versions, allowing the figures and assumptions to be compared with a high degree of accuracy, and
3) worldwide, it is one of the most sold cars and hence represents a mass-marketed car for the average car owner.
Why these grids?
We selected a variety of grids, from clean to dirty, to examine the effect that the location of ownership has on ultimate carbon emissions. California is of interest due to its perceived climate leadership position in the U.S. California is one of the cleanest grids in the U.S. with an estimated 47% renewable production (including hydro). We have chosen Wyoming because it relies heavily on coal and is, according to the EIA, one of the top five dirtiest states in terms of CO2 emissions per kWh produced. Similar to California, Germany is perceived to be a leader in the renewables space, but interestingly still operates many of its existing coal plants. Finally, we have analyzed an ideal scenario in which the grid produces energy in a 100% CO2 free capacity to establish an upper bound of EV benefits
Our calculations
After compiling all the data (see info on our sources in the appendix), we standardized the information to the metric of g CO2/100 km, as can be seen below:
We can see that electric cars start with a disadvantage, since their production emissions are significantly higher than those of regular ICE cars, which is largely due to the energy intensive battery production process. Note that the disadvantage varies widely — sources noted incremental CO2 emissions from 1 to 6 tons for EVs in comparison to ICE vehicles, with the difference primarily attributable to battery size.
We have then plotted lifetime emissions of various models of the VW Golf in the aforementioned regions. The resulting graph can be seen below, with a red circle around the areas points in which the electric versions reach emission parity with the diesel version respectively:
As Diesel vehicles are deemed to be “greener”, we have also calculated after how many kms EVs become less CO2 intensive on a total-lifecycle basis. This can be seen in the resulting calculations below:
We found that the an EV driven in California would only require 26,520 km driven for the total lifecycle CO2 impact to be less than its diesel counterpart. For context, the average American drives just over 21,000 km / year, which would imply an “EV Parity Period” of approximately of 15.2 months.
Germany’s grid results in more CO2 per kWh produced than California, which results in 43,676 km driven to reach parity with a Golf TDI. On average, Germans drive much less than Americans, an estimated ~14,000 km / year. Incorporating this lower annual distance driven, the EV Parity Period is elongated to 37.4 months, however this period is still well below the average life of a passenger automobile. Finally, our calculations based on the Wyoming grid show that at no point is it better to drive an EV due to the CO2 intensity of Wyoming’s electricity production.
If we assume that a car’s lifetime km driven amounts to 150,000 km, the CO2 emissions are as follows:
These numbers also show a clear picture, with EVs being the less carbon-intensive option in California and Germany in spite of the carbon disadvantage in production, but not in Wyoming, regardless of production. We assume the same lifetime for ICEs and EVs, although EVs are expected to have longer motor lifetimes thanks to their relative simplicity in design. However, EVs have not been on the market for long enough to be sure about the longer lifetime, which is why we have decided to use the same assumptions for ICE and EV:
Our analysis yields a variety of insights. We found that the carbon emissions due to the resource mix of the grid plays a key role for the effect of vehicle electrification on carbon emissions:
- In California, EVs save CO2 after only 26,000 km
- in Wyoming, a Diesel car always emits less carbon than an electric car.
- In Germany and California, every EV will save a significant amount of CO2 over its lifetime compared to both diesel and gas variants.
This means that parity depends highly on the cleanliness of the grid use to recharge EVs.
Implications of our findings:
The fact that in Wyoming an electric car essentially emits more CO2 than diesel cars highlights the importance of grid decarbonization. Once this is even partially complete, electric cars will shift from being energy consumers of a highly fossil fuel-reliant grid to a net gain to society after a varying amount of miles driven. The higher the penetration of renewables, the less time it takes for electric vehicles to reach emissions parity with their traditional fuel counterparts. Policy should therefore focus on both vehicle electrification and grid decarbonization. One without the other will not achieve much, as can be seen in Wyoming.
Another important consideration will be the timing of EV charging (solar energy peaks during the early afternoon hours when demand for electricity is low and often needs to be curtailed in California) Furthermore, where and how we source our materials will be an important consideration for the overall emissions and impact of the global supply chain — cobalt mining is an issue that is frequently mentioned here.
Our study took a holistic, yet simplified approach to understand the real impact of driving EVs. We found that in all but the most extreme regions in the US and Germany, the embedded energy and emissions are already lower that ICE vehicles. At the same time we have highlighted the important link between transportation and grid decarbonization. We are happy about any feedback you might have. We have added our sources and calculations below.
Appendix
Our calculations — feel free to comment
Our sources
We have used and benchmarked different sources for the different inputs:
- Fuel consumption: We used the actual fuel usage data from Spritmonitor.de,3 which is a website that allows people to enter their actual observed consumption. This datasource is deemed more reliable than manufacturer data, as it reflects real road conditions and usage patterns.
- Electricity consumption: Although spritmonitor.de also offers electricity consumption data for the VW e-Golf, we decided not to use their data, because their data on electricity is still relatively sparse and does not include charging losses. We instead decided to utilize ADAC test data.4 ADAC is the automotive association of Germany and a highly trusted source. The data set includes charging losses and reflects everyday usage patterns.
- Grid emissions: These are taken from the official governmental sources, such as the U.S. Energy Information Administration and the Umweltbundesamt.
- Production emissions: Estimating production emissions is challenging for a variety of reasons. Firstly, EVs come in many shapes and sizes, as do traditional ICE vehicles. A small, low-range EV may only cause moderately more CO2 during the production process, while a long-range could result in over 50% additional CO2 emissions. This assumption is also highly sensitive to factory location, which is nuanced by manufacturer and supply chain design. We ultimately decided to utilize estimates from LowC VP, which resulted in data that was directionally correct with other data sources, though none with enough specificity to be certain regarding VW Golf emissions. If the study was further pursued, it would be worth considering emissions on a manufacturer-level basis.
