What is the difference between well-to-tank and tank-to-wheel?

Well-to-tank is the emissions from producing and delivering a fuel or electricity; tank-to-wheel is the emissions from using it in the vehicle. Well-to-wheel is both together.

Do electric trucks have zero emissions well-to-wheel?

No. They have zero tank-to-wheel emissions, but generating and delivering the electricity emits greenhouse gases, which appear in well-to-wheel figures.

Are US EPA transport emission factors well-to-wheel?

No. The EPA says its transport factors represent combustion emissions only — tank-to-wheel — and not upstream or well-to-wheel emissions.

Term

Well-to-wheel (WTW) emissions

Well-to-wheel (WTW) emissions cover a fuel's whole path into use: well-to-tank (WTT), from producing and delivering the fuel or electricity, plus tank-to-wheel (TTW), from burning it in the vehicle. UK government factors for 2026 put diesel at 2.58 kg CO2e a litre tank-to-wheel and 0.61 well-to-tank — 3.19 well-to-wheel.

Also called WTW, well-to-tank, WTT, tank-to-wheel, TTW, well to wheel emissionsUpdated 13 October 2026

The two halves

Part	What it covers	kg CO2e per litre
Well-to-tank (WTT)	Upstream emissions from producing the fuel	0.61101
Tank-to-wheel (TTW)	Direct emissions where it is used	2.58354
Well-to-wheel (WTW)	WTT + TTW	3.19455

UK DESNZ greenhouse gas conversion factors 2026 — diesel, average biofuel blend

The definitions are the UK government's: WTT is upstream emissions from the production of fuel or electricity, TTW is direct emissions at the point of use, and WTW is the two added. Factor sets differ in what they include: the US EPA's emission factors hub says its transport factors are combustion only — tank-to-wheel — and do not include upstream or well-to-wheel emissions. Pure mineral diesel is 2.66155 kg CO2e a litre tank-to-wheel in the UK set; the 2.58354 figure reflects the biofuel blended into forecourt diesel.

Why it matters for electric trucks

A battery-electric truck has no tailpipe, so its tank-to-wheel figure is zero — but its emissions have moved upstream, to electricity generation, transmission losses and the well-to-tank share of the fuels power stations burn. Comparing a diesel truck's tank-to-wheel figure with an electric truck's makes the electric truck look like zero; comparing well-to-wheel is fair to both. The UK guidance also warns against double counting electricity used by vehicles.

Worked example: a year of one truck's diesel

30,000 litres × 2.58354 = 77,506 kg CO2e tank-to-wheel · 30,000 × 0.61101 = 18,330 kg well-to-tank · total 95,837 kg well-to-wheel — about 24% more than the tailpipe alone

UK DESNZ 2026 factors; the 30,000 litres is illustrative.

The mistake people make

Mixing bases. A carrier quoting tank-to-wheel and another quoting well-to-wheel can differ by a quarter for the same diesel. The UK guidance says an organisation should decide whether to include well-to-tank emissions and apply that consistently across every fuel and activity — and a buyer comparing carriers should ask which basis each used.

FAQ