Well-to-wheel emissions
Greenhouse gas emissions of a vehicle from producing and delivering its energy (well-to-tank) plus using it in the vehicle (tank-to-wheel), per unit distance.
Well-to-wheel (WTW) analysis compares vehicles on the full fuel or electricity chain, rather than tailpipe emissions alone. It splits into:
- Well-to-tank (WTT): extraction, refining, transport and distribution of fuel, or generation and transmission of electricity, including grid losses and charging losses
- Tank-to-wheel (TTW): combustion emissions in the vehicle (zero for BEVs and FCEVs)
Petrol: about 2.3 kg CO2/L at tailpipe + about 0.5–0.6 kg CO2e/L upstream
BEV: consumption (kWh/km) x grid carbon intensity (g/kWh)
Example: 0.17 kWh/km x 300 g/kWh ≈ 51 g/km vs petrol 6.5 L/100 km ≈ 185 g/km WTW
The JRC-EUCAR-CONCAWE (JEC) consortium publishes the standard European WTW study; Argonne's GREET model is the US reference. WTW excludes vehicle and battery manufacturing, so it differs from full lifecycle emissions (cradle-to-grave). Battery production adds roughly 50–100 kg CO2e per kWh of capacity depending on factory electricity (IEA, ICCT), a "carbon debt" a BEV typically repays within 1–3 years of driving in Europe.
For electricity, results depend on whether average or marginal carbon intensity is used. For hydrogen and e-fuels, upstream emissions dominate and vary enormously by production route.
Related terms
All terms →- Lifecycle emissions
Total greenhouse gas emissions of a product or power source across its full life, from raw material extraction and manufacturing through operation to decommissioning.
- Carbon intensity of electricity
The mass of CO2 (or CO2e) emitted per unit of electricity generated or consumed, usually expressed in grams per kilowatt-hour (gCO2/kWh).
- Battery electric vehicle (BEV)
A vehicle propelled solely by electric motors powered from an on-board rechargeable battery, with no internal combustion engine.
- EV efficiency (kWh/100 km)
The electrical energy an electric vehicle consumes per distance, usually in kWh/100 km or Wh/km (Europe) or miles/kWh and MPGe (US).
- Fuel cell electric vehicle (FCEV)
An electric vehicle that generates its electricity on board from hydrogen in a fuel cell, emitting only water vapour at the tailpipe.
- CO2e (CO2 equivalent)
A common unit that expresses emissions of different greenhouse gases as the mass of CO2 that would cause the same warming over a chosen time horizon.