Closing the growing PHEV loophole

Official real world usage data from plug-in hybrid vehicles (PHEVs) has long been documented, and has proven that real world emissions are multiple times higher than official values. T&E analysis of the latest 2023 real world data shows this gap has now grown to a factor of five.

This has misled consumers about PHEVs’ actual emissions and fuel efficiency, and it has allowed carmakers to use PHEVs as compliance vehicles and significantly weaken their CO₂ targets by passing off the vehicles as low emissions. To correct this, the EU has updated the assumption about the share of electric driving (utility factors, or UF) to better align the official CO₂ ratings with what the vehicles emit in the real world. The UF will adjust upward until 2028 to gradually close the gap between real-world and official emissions.

Since 2021, the European Environment Agency (EEA) has collected data from fuel monitors to inform the decision about which UF to set. T&E has analysed the EEA data from 2023, which includes 127,000 PHEVs. The analysis finds:

• The real-world CO₂ emissions of PHEV models registered in 2023 are nearly five times higher than the official emissions. This real world gap has been widening over the years from 3.5 in 2021 to 4.9 in 2023 based on official data transmitted from on-board fuel consumption meters (OBFCM).

• The gap is mostly caused by flawed assumptions on the share of electric driving mode (the ‘utility factor’, UF) which leads to a drastic underestimate of official PHEV emissions.

• It is welcome that the UF values are being corrected. But even with the planned 2027/28 UF correction, PHEV real-world emissions would be 18% higher than the official figures.

To find out more, download the analysis.