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Plug-in hybrid cars emit almost five times greater global warming emissions than official data indicate, as per a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy organization. This differs significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” said a senior analyst involved in the study. “That gap is widening and creates a serious problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. The team found that only 27% of driving was done in EV mode, whereas official assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were well above lab estimates. This occurred because EV motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled several major automaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in operating expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Hybrid cars have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with large automotive manufacturing.

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

An external energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which parts of the automotive industry argued there was insufficient information to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional cars,” they stated. “All policy changes concerning PHEVs should be made with utmost caution and in the light of this evidence.”