ViggoDifference  How We Calculate Our CO₂ Savings
3. April 2020
Patrick Pereira
We have an updated blogpost with more truthful calculations, you can find it here HERE
Here at Viggo, we are often asked a couple of questions:
 Are electric cars really better for the environment?
 Should the production of the electric car’s battery not be part of the CO₂ emission calculation?
 Don’t you have to drive a lot of kilometers before it makes sense to drive an electric car?
All very relevant questions if you want to know the facts behind the green transition.
At Viggo, we take pride in having our facts straight  so naturally, we have done thorough research into calculating the savings of CO₂emission that result from driving with us as opposed to driving with a regular diesel taxi.
In this post we will elaborate on the methods we have used to get the numbers that form the foundation of ViggoDifference  our CO₂ counter that is installed in all taximeters.
Why we believe electric cars are the future
We believe that the electric car is the future  and so do researchers, universities and many other institutions around the world.
In the current situation, electric cars emit less CO₂ (in carbon dioxide equivalents) than a normal diesel car  and at the same time, the percentage of sustainable energy is on the rise throughout the world. The more sustainable the energy we charge our cars with, the more sustainable the cars will become. For this reason we really believe that the electric car is a key element in a future with better opportunities for sustainable mobility.
But how do you then compare electric cars with diesel cars? Every car production will inevitably leave a CO₂ mark due to materials and production, but also the use of the car.
Below is a list of the different elements that need to be accounted for in the CO₂ calculations of the two types of cars  diesel and electric:
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 “energy mix”. The term “energy mix” covers how much of our energy originates from sustainable energy sources (such as sun and wind), and how much originates from fossil fuels.
A wellrecognised method for these types of analyses is the Life Cycle Analysis (LCA). The LCA is an analysis of the total CO₂ emissions during the car’s lifespan, in which you divide the total CO₂ emission with the number of kilometers the car drives throughout its lifespan. By doing so, you can make an estimate of the difference for each kilometer driven.
“CO₂” or “CO₂equivalents”?
When you talk about climate footprint, it is practical to use a common measuring unit. A lot of different kinds of greenhouse gases exist  the three primary ones are CO₂, methane and nitrous oxide. Methane and nitrous oxide are in these calculations converted to the effect they would have in CO₂equivalents. This is done simply to avoid complicating the calculations unnecessarily, so we can use a single measuring unit.
The correct way of informing about emission of greenhouse gases is actually “CO₂equivalents” but in our conclusions we often just use CO₂.
The two studies
To avoid relying on one single source for our calculations, we have used numbers from two different methods.

Calculation with data from Ellington et al, The International Council for Clean Transportation and Mercedes
For the electric car, we have made a calculation based on the peerreviewed study Ellington et al, along with an analysis made by The International Council for Clean Transportation (ICCT). The Ellington et al analysis has also been applied in the calculations for the diesel car, in which we have borrowed the official numbers from Mercedes. 
Calculation with data from Luxembourg Institute of Science and Technology (LIST)
LIST has made a calculator that shows how much CO₂ is emitted by different kinds of cars. They have also based their numbers on the analysis made by The International Council for Clean Transportation (ICCT) after which they have adjusted it with forskning.no’s calculator in order to account for the reduction of battery range during winter times.
Premises for both calculations
In order to understand the composition of an LCA, it is important to know the premises and assumptions we have used.
So we have chosen to compare a Tesla Model 3 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.
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.
Calculation with data from Ellington et al
In the calculation below, you can see the numbers we have pulled from the different studies and adapted to match our circumstances (300.000 kilometer lifecycle and the Danish energy mix).
TOTAL EMISSIONS  BASED ON ELLINGTON  

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  22 
Battery production  0  0.00  0  11250  0.04  38 
Tanktowheel electric  7067  0.02  24  
Tailpipe/tanktowheel  42000  0.14  140  
Total  52600  0.18  175  24817  0.08  84 
According to these calculations, the diesel car emits approximately 192g CO₂equivalents per kilometer and the Tesla emits 107g CO₂equivalents per kilometer.
So the difference between each kilometer driven is then 192107 = 85g CO₂equivalents per kilometer.
Calculation with data from LIST
In the calculation below, you can see the numbers we have pulled from LIST:
ANALYSIS BY LIST NUMBERS  

MercedesBenz C220D  Tesla Model 3  
Production & maintenance  23.999  g CO₂/km  24.2  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  59.43  g CO₂/km 
Total emissions by km  192.169  g CO₂/km  107.43  g CO₂/km 
Conclusion
According to our calculations based on the data from the two sources, you save between 85g  92g of CO₂ per kilometer driven, when you choose a Tesla Model 3 instead of a MercedesBenz C220D
Again, we have used the more conservative estimate.
Thus the reason behind the number  85g  that we use in our ViggoDifference counter.
And since we have been conservative with every estimate, it is likely that in reality, you save a little more by choosing a Viggo compared to a regular diesel car.
Also, in this calculation we have only focused on the climate footprint.
Another important factor to consider in our mobility choices is the CO₂ emissions from the tailpipe of the diesel car  which impacts the air pollution and thus our quality of life in urban areas. As this is an urban air quality measurement though, we have not included this in our calculations.
If you have any questions related to our calculations, you are more than welcome to get in touch with us.