What "well-to-tank" covers
The gas in your boiler and the diesel in your vans had a carbon cost before they reached you. Oil and gas were extracted, processed or refined, and transported to you. The government's methodology paper calls these the emissions "upstream from the point of use of the fuel": extraction, transport, refining, purification or conversion, and distribution. The name comes from transport: from the oil well to the fuel tank.
Electricity has well-to-tank emissions too. The gas and other fuels burned in power stations had to be produced and delivered, so each kWh you use carries a share of that supply chain.
Which scope?
Burning the fuel is Scope 1 (or Scope 2 for electricity). Producing it is someone else's direct emissions, so for you it is Scope 3. The GHG Protocol puts it in category 3, fuel- and energy-related activities, which covers the upstream emissions of the fuels you buy, the upstream emissions of the fuels behind your electricity, and the electricity lost in the grid. Our post on transmission and distribution losses covers that last part.
PPN 006's minimum Scope 3 list is categories 4, 5, 6, 7 and 9, and SECR is built around Scope 1 and 2, so neither requires well-to-tank. A full GHG Protocol Scope 3 inventory includes it.
The 2026 factors
| Fuel | Burning it (Scope 1 or 2), kg CO2e | Well-to-tank (Scope 3), kg CO2e | Uplift |
|---|---|---|---|
| Natural gas, per kWh | 0.18231 | 0.03021 | 17% |
| Grid electricity, per kWh | 0.13096 | 0.04041 | 31% |
| Diesel (forecourt), per litre | 2.58354 | 0.61101 | 24% |
| Petrol (forecourt), per litre | 2.075 | 0.58094 | 28% |
| Heating oil (kerosene), per litre | 2.54016 | 0.53078 | 21% |
The electricity row includes the well-to-tank share of grid losses as well as of generation. Its uplift looks large because the grid factor itself is now low; see why the UK grid gets cleaner every year.
A worked example
A small firm uses 40,000 kWh of gas, 30,000 kWh of electricity and 6,000 litres of diesel in its vans in 2026:
| Activity | Scope 1 or 2, tCO2e | Well-to-tank, tCO2e |
|---|---|---|
| 40,000 kWh of gas | 7.29 | 1.21 |
| 30,000 kWh of electricity | 3.93 | 1.21 |
| 6,000 litres of diesel | 15.50 | 3.67 |
| Total | 26.72 | 6.09 |
Well-to-tank adds 6.09 tonnes, about 23% on top of the Scope 1 and 2 total. No new data was needed: it is the same kWh and litres multiplied by a second factor.
Things that trip people up
- Adding it into Scope 1. Keep it in Scope 3. Mixing it in makes your Scope 1 look bigger than other firms' and breaks comparisons.
- Including it one year and not the next. Decide once, say so in your method note, and keep it the same, or your total jumps for no real reason.
- Forgetting travel and freight. Business travel, commuting and freight have well-to-tank factors too. The fuel is bought by someone else, so the emissions are Scope 3 either way.
- Assuming biofuels have none. Biofuels have low direct factors but real supply chain emissions. Our post on HVO shows how large they can be.
The real-world point
Well-to-tank is a reminder that every litre or kWh you save cuts emissions twice: once where it is burned and again in the supply chain behind it. In the example above, each litre of diesel saved avoids 3.19455 kg CO2e in total, not just the 2.58354 kg in Scope 1.
How Carbon Recycling helps
Well-to-tank is a single setting in Carbon Recycling. Switch it on and every gas, fuel, electricity, travel and freight entry gets its matching well-to-tank line from the same year's government set, filed in Scope 3, with category 3 for the fuel and energy you buy and travel and freight lines kept in their own categories. Changing the setting recalculates every existing entry, so all your years stay on the same basis. To see the uplift for your own bills first, tick the Scope 3 box in the free kWh to CO2e calculator, and see the guide to the 15 Scope 3 categories for where category 3 sits.