Calculates carbon emissions resulting from the use of cars. The calculation is carried out either by specifying the vehicle category (e.g. “middle class”) or by supplementing the data with the individual average consumption and fuel type. The emission factors for the calculation are taken from recognised scientific databases. In addition to the direct emissions resulting from the combustion of fuel, indirect (upstream) emissions resulting from the production and distribution of fuels are also taken into account. Greenhouse gas emissions resulting from the manufacture of the vehicle are not considered. ​

The combustion of one litre of fuel always causes the same amount of carbon emissions –  regardless of which vehicle or engine technology is used to burn it. This also applies to gas-powered vehicles that run on natural gas or LPG, for example. Therefore, for a precise carbon calculation, only the real consumption of the vehicles and the type of fuel are decisive. Other factors – such as the EU standard for vehicles or the year of construction –  are also not decisive for the carbon calculation, since carbon emissions – unlike nitrogen oxides –  cannot be reduced by filter systems or engine cleaning technology. ​

Analogous to the calculation of vehicles with combustion engines, the calculation of carbon emissions from electric vehicles is based on real consumption (in kWh/100 km) and the type of electricity generation. If vehicles are operated with 100 percent green electricity, there are no direct carbon emissions for use. Only indirect carbon emissions that result from the manufacture of the power plants and the provision of the electricity are taken into account (so-called “upstream emissions”). Therefore, even an electric car powered by 100 percent green electricity produces a small amount of carbon emissions. For vehicles that are not powered 100 percent by green electricity, the national electricity mix is used for the calculation. This is updated annually and is currently just under 500g CO2/kWh in Germany. In addition, we consider the indirect carbon emissions from electricity generation (“upstream emissions”). ​

When calculating hybrid vehicles, two cases must be distinct:  ​

• 1) Plug-in hybrid vehicles: Plug-in hybrid vehicles have an electric motor with external charging capability and a combustion engine.
• 2) For the carbon calculation, the consumption of primary fuel (e.g. diesel) is taken into account and the electrical component is automatically considered on the basis of corresponding average values.
• 3) For the calculation, therefore, only the consumption of the respective primary fuel has to be specified.
• 4) Other hybrid vehicles: Hybrid vehicles without their own charging facilities are considered based on their consumption of primary fuel.