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PHEVs produce nearly 5x more global warming emissions than official data show, as per a recent analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. That differs significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 cars registered in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a senior researcher participating in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to overall mileage. The team found that only 27% of travel was completed in EV mode, while lab estimates assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above official projections. This happened because EV motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions allowed four major carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more per year in operating expenses than would be assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car industries.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

An external energy economics specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient information to accurately assess actual emissions.

“The results show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering that evidence.”