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Plug-in hybrid cars emit almost 5x greater global warming pollution than official data show, as per a recent analysis.

Growing Discrepancy In Official and Real-World Emissions

Data shows that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit organization. That contrasts sharply with lab tests, which suggested a three-quarters decrease in pollution.

Researchers studied information from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “This discrepancy is widening and poses a serious problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in battery power compared to overall mileage. They found that just 27% of driving was completed in electric mode, while lab assumptions assumed 84%.

Even, when running in electric mode, pollution levels were well above lab estimates. This happened because electric motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for nearly a third of the distance covered in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in running costs than is estimated under lab tests.

“The strong statements that automakers often promote about their PHEV vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with significant automotive industries.

Some senior officials have proposed PHEVs as a possible “flexibility” solution to include in the legislation.

One independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after years in which segments of the car industry claimed there was too little information to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that data.”