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Plug-in hybrid cars release nearly five times greater global warming pollution than official figures indicate, according to a recent analysis.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts sharply with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are falling,” stated a lead analyst participating in the report. “That discrepancy is widening and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery mode compared to overall distance. They found that only 27% of travel was done in electric mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than official projections. That happened because EV motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 extra per year in operating costs than is assumed under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into political discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with significant automotive industries.

Several high-level officials have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive industry claimed there was too little information to properly assess real-world emissions.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with utmost care and in the light of that data.”