CO₂ per kWh is a measure of carbon intensity that shows how much carbon dioxide (CO₂) is associated with producing or consuming one kilowatt-hour (kWh) of electricity. It is typically expressed as gCO₂e/kWh and is widely used to estimate the emissions impact of EV charging, electrified fleets, and electricity-consuming operations.
What is CO₂ per kWh?
CO₂ per kWh represents the emissions linked to electricity generation. The value depends on the energy sources feeding the grid (renewables, nuclear, gas, coal), and can vary by:
– Country or bidding zone
– Time of day (due to changing generation mix)
– Season (heating demand, renewable output)
– Whether the value is average or marginal
In EV charging, CO₂ per kWh is used to estimate how much charging contributes to (or avoids) emissions compared to gasoline or diesel driving.
Why CO₂ per kWh Matters for EV Charging
CO₂ per kWh influences:
– The reported emissions of charging sessions and fleets
– CO₂ savings reporting compared to internal combustion vehicles
– Sustainability claims such as “low-carbon charging.”
– Corporate Scope 2 reporting for owned charging operations
– The value of smart charging strategies like carbon-aware charging
For networks operating across multiple countries, CO₂ per kWh is a key metric for comparing climate impact across markets.
Average vs Marginal CO₂ per kWh
There are two commonly used approaches:
Average Carbon Intensity
Average CO₂ per kWh reflects the overall emissions intensity of electricity generation over a period (hour/day/year).
– Common for reporting and footprint calculations
– Easier to apply at the portfolio scale
– Good for annual sustainability reporting and comparisons
Marginal Carbon Intensity
Marginal CO₂ per kWh estimates the emissions impact of an additional kWh of consumption at a specific moment.
– More relevant for operational optimization and demand response
– Often used in carbon-aware charging and real-time scheduling
– Can differ significantly from average values during peak times
How CO₂ per kWh Is Used in Charging Calculations
A basic charging emissions estimate is:
– Charging emissions (kgCO₂e) = kWh delivered × (gCO₂e/kWh ÷ 1000)
For example, if a session delivers 40 kWh and the grid intensity is 250 gCO₂e/kWh:
– 40 × 0.25 = 10 kgCO₂e
More advanced approaches adjust for:
– Charger efficiency and losses
– On-site renewable generation and clean energy matching rules
– Time-of-use emissions profiles (hourly factors)
CO₂ per kWh and Renewable Electricity Claims
A lower CO₂ per kWh can come from:
– A grid with high renewable/nuclear share
– On-site solar generation used for charging
– Renewable procurement and certificate-based matching
However, claims must clearly define whether they reflect:
– Physical grid intensity at the time of charging, or
– Accounting-based matching using energy attribute certificates
Clear boundaries prevent confusion and double-counting.
Typical Data Sources for CO₂ per kWh
Organizations usually obtain CO₂ per kWh values from:
– National grid operators or official energy agencies
– Electricity suppliers (contract-specific factors)
– Carbon accounting databases used for Scope 2 reporting
– Real-time grid intensity providers for hourly optimization
The choice of source should match the reporting purpose and required auditability.
Common Pitfalls
– Mixing average and marginal factors without stating which is used
– Using annual national averages to claim real-time “green charging.”
– Ignoring geographic boundaries (using a factor from a different market zone)
– Not documenting the data source, timeframe, and methodology
– Treating certificate-based matching as identical to real-time grid intensity
Related Glossary Terms
Carbon Intensity
Carbon-Aware Charging
Clean Energy Matching
Energy Attribute Certificates
Carbon Footprint Reporting
CO₂ Savings Reporting
Renewable Integration
kWh Delivered per Charger