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

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. This differs significantly with lab tests, which assumed a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand cars sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a senior analyst participating in the report. “That discrepancy is growing and poses a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the percentage of miles travelled in electric mode relative to total mileage. They found that only a quarter of travel was done in electric mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above official projections. That happened because EV motors were not strong sufficient to function alone, resulting to combustion motors using gasoline for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in operating costs than would be estimated under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with significant car industries.

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

One external energy economics expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which segments of the automotive sector claimed there was insufficient information to accurately assess actual emissions.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert stated. “All policy changes concerning PHEVs should be made with extreme caution and in the light of this data.”