Calculating our CO₂ savings
20. November 2020
Patrick Pereira
Back in April 2020, we launched our CO₂ counter in the cars  so you can keep track of your personal CO₂ savings on the taximeter during your Viggo trip.
Since we published the latest calculations, new knowledge and new figures have been published about Denmark's electricity mix in 2019. These new figures naturally have an impact on the CO₂ savings we have calculated.
The Danish electricity mix in 2018 emitted 212 g CO₂ / kWh. In 2019, the number was further lowered to just 135 g CO₂ / kWh.
In conclusion, this prompted us to review our calculations, and below is a brief review of the method used as well as our sources.
Comparison of a diesel car with an electric car  the Life Cycle Analysis
Every car production has a CO₂ footprint  both in the form of materials used, but also in the form of the electricity used to produce the individual car. On top of this comes the use  of either electricity for the battery or fossil fuels for the internal combustion engine.
By taking the total emissions from both production and use and dividing this by the number of km driven over a car's "lifetime", you can find the CO₂ that is emitted per km.
We have used a socalled Life Cycle Analysis (LCA) to calculate CO₂ emissions per km driven in the two different cars. The calculation looks like this:
CO₂emissions per km = (emissions from production + emissions from driving) / amount of km driven
Emissions from production = battery+car production + car maintenance
Emissions from driving = energy use in kWh per km * CO₂emissions per kWh
Apart from these simple formulae, below is a further explanation of the various terms:
Diesel car

Car production
Covers all the emissions from producing the different parts of the car

Upstream emissions
Covers the emissions related to sending out fossil fuels to the gas (petrol) station

Tanktowheel
Covers the emissions from the fuel used in the car for driving
Electric car

Car production
Covers the emissions from the entire car production except the battery

Battery production
The CO₂ emissions from producing the battery

Upstream emissions
The CO₂ emissions related to transmitting the energy to the charging station

Tanktowheel
Covers the emissions from the energy used in the car. These emissions depend on the Danish “electricity mix”. The term electricity mix covers how much of our electricity originates from renewable sources (such as sun and wind), and how much originates from fossil fuels.
Assumptions
The basic assumptions of any calculation is important for the outcome  and below is a list of ours:

Choice of car
We have chosen to compare a Tesla Model 3 Long Range with a smaller diesel car often used as a taxi, MercedesBenz C220D. Both models are used regularly as taxis but in order to be on the more conservative side with our calculations, we have chosen a diesel car which is slightly smaller than the Tesla Model 3.

Lifecycle
A taxi drives a lot of kilometers during its lifespan. We have made a relatively conservative estimate and based our calculations on 300.000 kilometers.

The Danish electricity mix
The Danish electricity mix depends on how much of our electricity comes from renewable sources such as solar and wind, and how much is extracted from fossil fuels. The Danish electricity mix was more sustainable in 2019 than in 2018, which resulted in emissions of 135 g CO₂/kWh.
Our sources for calculating CO₂ emissions by the various cars
To avoid "cherrypicking" our data, we have consulted figures from three different studies:

Ellington et al, The International Council for Clean Transportation og Mercedes
For the electric car, we have made a calculation based on the peerreviewed study Ellington et al, as well as an analysis made by The International Council for Clean Transportation (ICCT). The Ellington et al analysis has also been used in the calculations for the diesel car, where we have also taken the official figures from Mercedes.

Luxembourg Institute of Science and Technology (LIST)
LIST has made a calculator explaining how much CO₂ is emitted by different car types. They have also based their figures on the analysis made by The International Council for Clean Transportation (ICCT) and the numbers have then been adjusted with forskning.no’s calculator for reducing the range of batteries in winter times (if you try the calculator, remember to edit the CO₂ emissions from the electricity mix, as their default is European numbers and not Danish).

Carbonbrief
Carbonbrief has in part also used ICCT, but has then added battery calculations from IVL Swedish Environmental Institute.
The Ellington et al calculation
Below you can see the calculation made from the numbers drawn from Ellington et al:
ELLINGTON ET AL  

MercedesBenz C220D  Tesla Model 3  
Total  kg  kg/km  g/km  Total  kg  kg/km  g/km  
Production & maintenance  10600  0.04  35  6500  0.02  21.7 
Battery production  0  0.00  0  11250  0.04  37.5 
Tanktowheel electric  5786  0.019  20.1  
Tailpipe/tanktowheel  42000  0.14  140  
Total  52600  0.18  175  23536  0.078  79 
The difference per km driven is therefore 17579 = 96 g CO₂ equivalents per km.
The LIST calculation
Below you can see the calculation made by LIST, available on their calculator:
LIST  

MercedesBenz C220D  Tesla Model 3  
Production & maintenance  23.999  g CO₂/km  25.4  g CO₂/km 
Battery production  0  g CO₂/km  23.8  g CO₂/km 
Welltotank  25  g CO₂/km  0  g CO₂/km 
Tanktowheel, corrected for by ICCT  143.17  g CO₂/km  0  g CO₂/km 
Welltotank, tank to wheel, incl. NEDC correction  0  g CO₂/km  22.4  g CO₂/km 
Total emissions by km  192.169  g CO₂/km  71  g CO₂/km 
The difference per km driven is therefore 19271 = 121 g CO₂ equivalents per km.
The Carbonbrief calculation
Below you can see the calculation made from the numbers drawn from Carbonbrief and edited with our assumptions:
CARBONBRIEF  

MercedesBenz C220D  Tesla Model 3  
Total  kg  kg/km  g/km  Total  kg  kg/km  g/km  
Production & maintenance  10600  0.04  35  5700  0.019  19 
Battery production  0  0.00  0  13200  0.04  44 
Tanktowheel electric  0  0.00  0  5786  0.020  20.1 
Tailpipe/tanktowheel  42000  0.14  140  
Total  52600  0.18  175  23536  0.078  83 
The difference per km driven is therefore 17583 = 92 g CO₂ equivalents per km.
Conclusion
According to our calculations based on data from the three sources, you save somewhere between 92 and 121 g CO₂ equivalents per km driven by choosing a Tesla Model 3 versus a MercedesBenz C220D.
The average of the three is 103 g CO₂ / km.
Therefore, the official savings we count is 103 g CO₂ / km.
As a side note, this calculation only includes the climate footprint. Aside from this, with tailpipe emissions from diesel cars, there is also a high level of air pollution, which affects our quality of life in cities  and this is an added value of the electric car.
If you have any questions regarding these calculations, you are of course always welcome to contact us.