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Plug-in hybrid electric vehicles release nearly 5x greater global warming pollution than lab-reported figures show, according to a new report.

Widening Gap In Lab and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit group. That contrasts sharply with lab estimates, which assumed a 75% decrease in pollution.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a lead analyst participating in the study. “This gap is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode relative to overall distance. The team determined that just 27% of driving was completed in electric mode, while official estimates suggested 84%.

Even, when running in EV mode, emission levels were significantly higher than official projections. That happened because electric motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating expenses than would be estimated under lab tests.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant car industries.

Some high-level politicians have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

An independent energy policy specialist, who was not involved with the research, called the report a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient data to properly assess actual CO2 output.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” the expert said. “Any policy changes concerning PHEVs should be implemented with extreme care and in the light of this evidence.”