Q: What is 'Well-to-Wheel' vs 'Tank-to-Wheel'?

'Tank-to-Wheel' emissions are the CO₂ produced only when driving the car. EVs have zero tailpipe emissions. 'Well-to-Wheel' includes all upstream emissions from producing the 'fuel'—like extracting oil, refining petrol, or generating electricity. Our calculator now optionally includes the battery manufacturing footprint to provide a more holistic, well-to-wheel comparison, which still consistently shows EVs have a significantly lower overall carbon footprint over their lifetime.

Question 1

How are CO₂ savings calculated?

Accepted Answer

The calculation subtracts the EV's annual emissions from the petrol car's annual emissions. The petrol car's emissions are calculated based on its fuel efficiency (MPG) and the standard CO₂ output per litre/gallon of fuel. The EV's emissions are calculated from the carbon intensity of the selected region's electricity grid. Optionally, it can include the amortized CO₂ cost of manufacturing the battery to give a more complete 'well-to-wheel' comparison.

Question 2

What are the data sources for the emissions figures?

Accepted Answer

This calculator uses official 2024 conversion factors. For the UK, it uses data from the Department for Environment, Food & Rural Affairs (DEFRA). For the US, it uses grid emission factors from the Environmental Protection Agency (EPA). For the EU, it uses an average from Eurostat. The battery manufacturing emissions are based on an industry-average figure of 75kg CO₂ per kWh of battery capacity.

Question 3

What is 'Well-to-Wheel' vs 'Tank-to-Wheel'?

Accepted Answer

'Tank-to-Wheel' emissions are the CO₂ produced only when driving the car. EVs have zero tailpipe emissions. 'Well-to-Wheel' includes all upstream emissions from producing the 'fuel'—like extracting oil, refining petrol, or generating electricity. Our calculator now optionally includes the battery manufacturing footprint to provide a more holistic, well-to-wheel comparison, which still consistently shows EVs have a significantly lower overall carbon footprint over their lifetime.

Question 4

How is the 'trees planted' equivalence calculated?

Accepted Answer

This is an illustrative metric to help visualize the impact. We use the widely-cited figure that a mature tree absorbs approximately 22 kilograms (about 48 pounds) of carbon dioxide per year. Your annual CO₂ savings are divided by this number to give an estimate of the equivalent carbon sequestration.

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EV vs Petrol: CO₂ Emissions Calculator

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