What are well-to-wheel emissions?
Well-to-wheel emissions cover two parts of a transport energy chain. Well-to-tank covers producing and delivering energy to the vehicle. Tank-to-wheel covers emissions released while the vehicle operates.
Why do well-to-wheel emissions matter to you?
Suppose a machinery maker in Germany compares a diesel company van with a battery-electric van for a customer. The customer may ask whether each figure in kilograms of carbon dioxide equivalent per kilometre (kg CO2e/km) covers vehicle operation only or the full energy chain. Zero tailpipe emissions for the electric van do not mean zero well-to-wheel emissions because generating and delivering its electricity can still cause emissions. Record each energy source, geography, factor year, kilometres travelled, and included stages.
How are well-to-wheel emissions calculated?
Use the formula: well-to-wheel emissions = well-to-tank emissions + tank-to-wheel emissions. Put both parts on the same basis, such as kg CO2e/km. For a company-owned petrol or diesel vehicle, fuel burned in the vehicle is Scope 1. GHG Protocol Formula 3.1 puts emissions from extracting, producing, and transporting that purchased fuel in Scope 3 Category 3. For a company-owned electric vehicle, electricity generation is Scope 2, while upstream energy stages and grid losses are Scope 3 Category 3. Well-to-wheel is a transport total, so do not report it as one corporate scope.
What mistakes should you avoid?
- Calling a zero-tailpipe vehicle zero-emission without counting how its electricity or hydrogen was produced.
- Adding factors with different units, years, geographies, vehicle classes, or energy pathways.
- Adding a separate well-to-tank factor to a factor that already includes the upstream chain.
- Calling well-to-wheel a full vehicle life-cycle result when vehicle manufacture and end of life are excluded.
Is well-to-wheel the same as life-cycle emissions?
No. The European Commission's JEC method limits well-to-wheel to the energy pathway and vehicle operation. A full life-cycle assessment can also count vehicle and infrastructure manufacture, maintenance, and end of life.
What should you send when a customer asks for well-to-wheel emissions?
Send the activity data, separate factors, units, source, year, geography, energy pathway, vehicle class, calculation, and final kg CO2e/km result. State which parts enter Scope 1, Scope 2, or Scope 3.