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Plug-in hybrid cars emit almost 5x more global warming emissions than official data show, as per a new analysis.

Growing Discrepancy Between Official and Actual Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This contrasts significantly with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” said a senior researcher involved in the study. “That gap is growing and creates a serious issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall distance. They found that only a quarter of driving was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, pollution amounts were well above lab estimates. That happened because electric motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for almost a third of the distance covered in electric mode.

Regulatory and Economic Consequences

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

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong claims that manufacturers 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 helping the environment and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been drawn again into political discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant automotive manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient information to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they said. “Any regulatory changes concerning PHEVs should be made with extreme care and considering this evidence.”