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Plug-in hybrid electric vehicles emit almost five times more planet-heating pollution than lab-reported data indicate, as per a recent report.

Widening Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit group. That contrasts sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined information from onboard energy use monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead analyst participating in the report. “This discrepancy is growing and poses a serious issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to overall mileage. They determined that only 27% of driving was done in electric mode, whereas lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to function alone, resulting to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 more annually in running costs than would be assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid cars have lately been brought again into policy debates as carmakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car industries.

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

One external energy policy expert, who was not involved with the study, described the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was insufficient information to properly assess actual emissions.

“These findings show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”