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Plug-in hybrid cars release almost 5x greater planet-heating emissions than official data show, as per a new analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a advocacy organization. This contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a serious problem. As a result, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric power compared to overall distance. They found that only 27% of travel was completed in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above lab projections. This happened because electric motors were insufficiently powerful enough to operate independently, resulting to engines using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled four major carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 extra per year in running costs than is assumed under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn back into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large car industries.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

One independent energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the automotive sector claimed there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they said. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this evidence.”