Carbon savings per session is a metric that estimates how much CO₂e is avoided when an EV charging session replaces an equivalent amount of driving that would otherwise have been powered by an internal combustion engine (ICE). It is typically reported as kg CO₂e saved per charging session, based on energy delivered (kWh), the carbon intensity of electricity, and an ICE baseline for the same mobility service.
What Is Carbon Savings per Session?
Carbon savings per session compares two emissions values for the “same service”:
– Baseline emissions: emissions that would have been produced by an ICE vehicle driving an equivalent distance
– Actual emissions: emissions associated with the electricity used in the EV charging session (and optionally charging losses)
The result is:
– Carbon savings per session = ICE baseline CO₂e – EV charging CO₂e
It can be calculated per individual session or averaged across a site/network.
Why Carbon Savings per Session Matters in EV Charging
This metric is useful for customer communication and reporting because it converts charging activity into an outcome people understand. It matters because it:
– Creates a clear KPI for dashboards and customer reports
– Supports ESG storytelling (with defensible methodology)
– Enables comparisons across sites and time periods when session data is available
– Helps demonstrate the value of low-carbon electricity sourcing
– Supports tender reporting where outcomes must be quantified
How Carbon Savings per Session Is Calculated
A practical calculation approach is:
– Measure session energy
– kWh delivered in the session (from charger data or billing-grade metering)
– Optional: include estimated charging losses if your boundary includes them
– Estimate EV distance served (optional but common)
– Convert kWh to km using an assumed EV efficiency (kWh/100 km)
– Or use vehicle-specific telematics if available (highest accuracy)
– Calculate EV session emissions
– EV CO₂e = kWh × electricity emission factor (kg CO₂e/kWh)
– Use location-based and/or market-based factors depending on reporting policy
– Calculate ICE baseline emissions for the same distance
– ICE CO₂e = km × ICE emission factor (kg CO₂e/km)
– Baseline can be a defined fleet vehicle class (car/van/bus) or an agreed benchmark
– Compute savings
– Savings = ICE CO₂e – EV CO₂e
Key Inputs and Assumptions
Carbon savings per session is sensitive to assumptions, especially if you don’t have vehicle-specific data:
– Electricity emission factor (varies by country and time period)
– EV efficiency (kWh/100 km) used to translate kWh into km
– ICE baseline (fuel type, vehicle class, g CO₂e/km)
– Whether you include charging losses and site overhead
– Whether the session is linked to a known vehicle type (fleet vs public unknown)
For public charging, many operators report savings using standardized assumptions and clearly disclose them.
Typical Use Cases
– Customer dashboards showing “CO₂e saved” after each charging session
– Fleet reporting where the vehicle type is known and savings can be calculated accurately
– Workplace charging reports showing average savings per employee session
– Municipal projects communicating outcomes for funded charging infrastructure
– Comparing sites: sessions at lower-carbon grids show higher savings per kWh delivered
Key Benefits of Carbon Savings per Session
– Easy-to-understand outcome metric for users and stakeholders
– Encourages better charging behavior (charging when the grid is cleaner)
– Supports premium “green charging” programs with measurable impact
– Can be automated at scale using back-end session data and emission factors
– Useful for marketing and sustainability reporting when methodology is transparent
Limitations to Consider
– Without vehicle data, savings are estimates and depend on assumed efficiencies and baselines
– ICE baselines vary widely; using a generic average can misrepresent specific fleets
– Savings may be lower if grid carbon intensity is high or charging occurs at high-intensity times
– “Saved emissions” should be separated from “emissions of charging” to avoid confusion
– Double counting risk exists if multiple parties claim the same avoided emissions
– Best used with clear disclaimers and consistent methodology versioning
Related Glossary Terms
Carbon Intensity
Carbon Intensity Tracking
Carbon Footprint
Carbon Footprint Reporting
Emission Factors
CO₂e
Billing-Grade Metering
Charge Detail Record (CDR)
Carbon Dashboards
Carbon Footprint Allocation