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PHEVs release almost 5x greater planet-heating pollution than lab-reported figures indicate, according to a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a senior researcher participating in the report. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to total distance. The team found that only 27% of travel was done in electric mode, while official assumptions suggested 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were not strong sufficient to function independently, leading to combustion motors burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 extra per year in operating costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from member states with significant automotive industries.

Several senior officials have proposed plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

One independent energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the automotive industry claimed there was insufficient data to accurately evaluate real-world emissions.

“The results show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “All policy changes regarding PHEVs should be implemented with utmost care and considering that data.”