Well-to-wheel vs. tank-to-wheel: a guide for businesses
Direct answer
Well-to-wheel (WTW) counts all CO2 emissions from the energy source to the turning wheel: the extraction, production and distribution of the fuel or electricity, plus its use in the vehicle. Tank-to-wheel (TTW) counts only the direct emissions from the vehicle itself, such as burning diesel in the engine. The difference between the two is the upstream chain, known as well-to-tank (WTT).
- Clear definition
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- Risks and opportunities visible
- Practical next steps
Well-to-wheel vs. tank-to-wheel: scattered information versus Energy Intelligence
On paper an electric lease car drives without emissions, while its electricity may have been generated in a gas-fired power plant. That gap between paper and practice comes from the chosen system boundary. For fleet managers, sustainability coordinators and finance leads, this choice determines how green an investment in electric or hydrogen vehicles looks in the annual report. Anyone comparing quotes, footprints or certification requirements should therefore first check which part of the chain has been counted. Otherwise you compare numbers that do not describe the same thing.
- For fossil petrol in the Netherlands, the current factors are around 2.4 kg of CO2 equivalent per litre tank-to-wheel and over 3 kg well-to-wheel; the upstream chain adds almost 0.7 kg per litre.
- Electric and hydrogen driving cause no tailpipe emissions; their real emissions sit entirely in the upstream chain and only become visible in well-to-wheel figures.
- The Dutch CO2 Performance Ladder uses the well-to-wheel factors from co2emissiefactoren.nl; organisations reporting scope 3 under the GHG Protocol may use tank-to-wheel for scope 1.
Insight
Traditional approach
Information is scattered across portals, documents, invoices or separate spreadsheets.
Modern approach
Data, context and interpretation are brought together into a clear decision picture.
Decision-making
Traditional approach
Choices are made based on averages, assumptions or occasional analyses.
Modern approach
Scenarios, KPIs and current measurement data make the trade-off more concrete and repeatable.
Follow-up
Traditional approach
Actions often stay non-committal or disappear into separate reports.
Modern approach
Follow-up actions, monitoring and reporting are linked to the same energy data.
What exactly does each boundary include?
Tank-to-wheel counts what happens in the vehicle itself: the combustion of diesel or petrol in the engine. Well-to-tank counts the upstream chain: extracting the oil, refining it into fuel and transporting it to the filling station. Well-to-wheel is the sum of the two and therefore covers the entire chain from energy source to turning wheel. The official Dutch list on co2emissiefactoren.nl publishes all three figures for every fuel. For fossil petrol the current factors are roughly 2.4 kg of CO2 equivalent per litre for combustion and almost 0.7 kg for the upstream chain, together over 3 kg well-to-wheel. Biogenic CO2 from biofuels is listed separately, so you can report it apart from your scope 1, 2 and 3 footprint.
- Well-to-tank (WTT): extraction, production and distribution of the energy carrier.
- Tank-to-wheel (TTW): the direct emissions from using it in the vehicle.
- Well-to-wheel (WTW): the sum of both, the full chain.
- The list on co2emissiefactoren.nl shows all three values per fuel.
Why is the gap so large for electric and hydrogen vehicles?
An electric car has no exhaust, so its tank-to-wheel emissions are zero. All emissions sit in the production of the electricity, including grid losses. How high they are depends strongly on the source: grey electricity gives a fundamentally different outcome than wind or solar power. With hydrogen the pattern is even stronger. Grey hydrogen made from natural gas has a substantial upstream footprint in production, while nothing comes out of the vehicle itself. Comparing an electric car on a tank-to-wheel basis with a diesel car on a well-to-wheel basis therefore means comparing apples with oranges. A fair comparison between drivetrains requires the same boundary, and for electric and hydrogen that is well-to-wheel in practice.
- Using electricity causes no direct (tank-to-wheel) emissions for the user.
- The well-to-wheel footprint of electricity depends on the source and includes grid losses.
- With grey hydrogen all emissions sit in production, none in the vehicle.
- Always compare drivetrains within the same boundary, or you compare apples with oranges.
Which boundary do you use when?
According to co2emissiefactoren.nl, the choice between tank-to-wheel and well-to-wheel depends on the goal of the inventory. If you only report scope 1 and 2 to assess reduction measures, well-to-wheel gives the fullest picture: those factors also show the upstream differences between fuels. If you follow the GHG Protocol and also report scope 3, you may use tank-to-wheel for scope 1. The upstream chain then goes into scope 3, category 3, fuel and energy related activities. This prevents multiple organisations from counting the same emissions in scope 1. The Dutch CO2 Performance Ladder prescribes the factors from co2emissiefactoren.nl and uses well-to-wheel values for fuels. The same list can also be used for CSRD reporting. For figures per passenger or tonne kilometre, CE Delft publishes the STREAM studies, which include both the upstream chain and vehicle use, in line with ISO 14083.
- Simple footprint covering scope 1 and 2 only: well-to-wheel gives the fairest picture.
- GHG Protocol with scope 3: tank-to-wheel in scope 1, the upstream chain in scope 3 category 3.
- Dutch CO2 Performance Ladder: the well-to-wheel factors from co2emissiefactoren.nl are prescribed.
- CSRD reporting can be prepared with the same Dutch emission factor list.
- CE Delft's STREAM studies provide comparable figures per transport mode, including the upstream chain.
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