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PHEVs release nearly 5x more planet-heating pollution than lab-reported data indicate, according to a recent analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit group. That contrasts significantly with lab estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead analyst involved in the study. “This discrepancy is widening and creates a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to overall distance. The team determined that just a quarter of travel was done in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab estimates. This happened because electric motors were not strong enough to function alone, leading to engines using fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four large automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more per year in running expenses than is estimated under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been brought again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant automotive industries.

Some high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient information to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert said. “Any policy changes regarding PHEVs should be implemented with extreme care and considering this data.”