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Plug-in hybrid cars release almost 5x more planet-heating pollution than official figures show, as per a recent analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. That contrasts significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts examined data from onboard energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found 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 emissions are increasing, while official figures are falling,” said a senior analyst participating in the report. “That gap is widening and poses a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total distance. The team found that only a quarter of driving was completed in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

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

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been brought back into policy discussions as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An external energy economics expert, who was not involved with the research, described the analysis a “very useful contribution” after years in which segments of the automotive sector argued there was insufficient information to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be implemented with utmost caution and in the light of that data.”