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PHEVs produce almost 5x more planet-heating emissions than lab-reported data show, according to a new report.

Widening Gap Between Lab and Actual Emissions

Data shows that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, based on research carried out by a non-profit organization. That differs sharply with lab tests, which assumed a three-quarters reduction in pollution.

Analysts examined information from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a senior analyst involved in the report. “That gap is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to total mileage. The team found that just a quarter of driving was done in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above lab estimates. That happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for almost a third of the travel covered in electric mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed several major carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra annually in running expenses than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive industries.

Some senior politicians have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One external energy policy specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was insufficient data to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “Any policy adjustments concerning PHEVs should be made with utmost caution and considering this data.”