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Plug-in hybrid cars produce almost 5x more global warming emissions than lab-reported data show, as per a new report.

Widening Discrepancy In Official and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy organization. This differs sharply with laboratory tests, which assumed a 75% decrease in pollution.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” stated a lead researcher participating in the study. “That gap is widening and poses a serious problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric mode compared to overall distance. The team determined that just a quarter of driving was done in electric mode, whereas lab estimates suggested 84%.

Even, when operating in electric mode, pollution amounts were well above official projections. This happened because electric motors were not strong sufficient to operate independently, leading to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more annually in running costs than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with large automotive industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the study, called the report a “very useful contribution” after years in which parts of the automotive industry claimed there was insufficient data to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that data.”