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gCO₂ avoided per session

What it means

gCO₂ avoided per session is an estimate of how many grams of CO₂ emissions were avoided because an EV charging session enabled electric driving instead of the equivalent distance being driven by a comparable internal combustion engine (ICE) vehicle.

It’s an “avoided emissions” metric (a counterfactual), so it depends heavily on the assumptions you choose.

A practical calculation method (most common)

  1. Convert session energy to electric distance
  • kmEV=Edelivered  (kWh)×ηEVcons  (kWh/km)\text{km}_{EV} = \dfrac{E_{delivered}\;(\text{kWh}) \times \eta}{EV_{cons}\;(\text{kWh/km})}kmEV​=EVcons​(kWh/km)Edelivered​(kWh)×η​

Where:

  • EdeliveredE_{delivered}Edelivered​ = energy delivered in the session
  • η\etaη = wall-to-wheel factor (optional; if you already use vehicle-side energy, set η=1\eta=1η=1)
  • EVconsEV_{cons}EVcons​ = EV consumption (kWh/km)
  1. Compute ICE emissions for that distance
  • gCO₂ICE=kmEV×ICEgCO2/km\text{gCO₂}_{ICE} = \text{km}_{EV} \times ICE_{gCO₂/km}gCO₂ICE​=kmEV​×ICEgCO2​/km​
  1. Compute EV charging emissions for that session
  • gCO₂EV=Edelivered  (kWh)×GridgCO2/kWh\text{gCO₂}_{EV} = E_{delivered}\;(\text{kWh}) \times Grid_{gCO₂/kWh}gCO₂EV​=Edelivered​(kWh)×GridgCO2​/kWh​
  1. Avoided emissions
  • gCO₂ avoided=gCO₂ICE−gCO₂EV\text{gCO₂ avoided} = \text{gCO₂}_{ICE} – \text{gCO₂}_{EV}gCO₂ avoided=gCO₂ICE​−gCO₂EV​

If the result is negative, it means (under your assumptions) the session caused more CO₂ than the ICE alternative.

Minimal version (when you only have session kWh)

If you don’t want to convert to km, you can express avoided emissions per kWh and multiply:

  • gCO₂ avoided≈Edelivered×(ICEgCO2/kmEVcons  (kWh/km)−GridgCO2/kWh)\text{gCO₂ avoided} \approx E_{delivered} \times \left(\dfrac{ICE_{gCO₂/km}}{EV_{cons}\;(kWh/km)} – Grid_{gCO₂/kWh}\right)gCO₂ avoided≈Edelivered​×(EVcons​(kWh/km)ICEgCO2​/km​​−GridgCO2​/kWh​)

Key assumptions you must define (or your numbers won’t be comparable)

  • ICE baseline: petrol vs diesel, vehicle class, real-world gCO₂/km (or L/100 km + fuel CO₂ factor).
  • EV consumption: fleet-specific or typical kWh/100 km (varies a lot by season, speed, payload).
  • Grid carbon intensity: location-based vs market-based; average vs time-of-use (hourly) intensity.
  • Losses boundary: are you using charger meter kWh, or vehicle battery kWh? (decide whether to apply η\etaη).
  • Attribution rule: do you assume the session enabled incremental EV km, or just replenished energy that would have been charged elsewhere?

Common pitfalls

  • Using tank-to-wheel ICE vs well-to-wheel EV (mixing boundaries).
  • Using national average grid intensity when the site uses renewable-backed supply (or vice versa) without stating it.
  • Claiming “avoided” when you can’t justify the counterfactual (better wording: “estimated avoided emissions vs baseline ICE”).

– Carbon intensity (gCO₂/kWh)
– CO₂ savings reporting
– Location-based vs market-based emissions
– Well-to-wheel (WTW) / tank-to-wheel (TTW)
– Session energy (kWh delivered)