Site owners and companies often want to state how much carbon their chargers save. A credible figure compares the emissions from the electricity used with the emissions from the fuel it replaced. Here is a simple, transparent method.
The calculation
- Energy delivered (kWh) from the charger's records.
- Distance driven = energy × vehicle efficiency (km per kWh).
- Fuel avoided = distance ÷ the fuel efficiency of the vehicle it replaced (km per litre).
- Fuel emissions avoided = litres avoided × the CO₂ emitted per litre of fuel.
- Electricity emissions = energy × the grid emission factor (kg CO₂ per kWh).
- Net saving = fuel emissions avoided − electricity emissions.
An illustrative example
These figures are assumptions for illustration. Use your own data and current emission factors.
| Step | Assumption | Result |
|---|---|---|
| Energy delivered per day | 150 kWh | 150 kWh |
| Distance driven | 7 km per kWh | 1,050 km |
| Petrol avoided | 15 km per litre | 70 litres |
| Fuel emissions avoided | About 2.3 kg CO₂ per litre | About 161 kg CO₂ |
| Electricity emissions | Assumed 0.7 kg CO₂ per kWh | 105 kg CO₂ |
| Net saving per day | About 56 kg CO₂ |
At that rate, one charger would avoid about 20 tonnes of CO₂ a year. With renewable electricity, the electricity emissions fall sharply and the saving rises.
Use the latest grid emission factor published by the Central Electricity Authority, and update it each year. The grid is getting cleaner, so savings from the same charger grow over time.
Keep it honest
- Show both sides of the calculation, not only fuel avoided.
- State every assumption and its source.
- Use conservative vehicle efficiency figures.
- Count only energy actually delivered, not charger capacity.
Other benefits
EVs also produce no tailpipe emissions where people live and work, which improves local air quality. That benefit is real even where the grid still relies on fossil fuels.