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PHEVs release nearly five times more planet-heating pollution than official data show, according to a new analysis.

Growing Gap In Lab and Actual Emissions

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on research carried out by a non-profit group. This differs sharply with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a lead researcher involved in the study. “That discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode relative to total distance. They found that only a quarter of travel was done in EV mode, while official assumptions suggested 84%.

Even, when running in EV mode, emission amounts were significantly higher than official projections. That happened because EV motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating expenses than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

An external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the automotive sector argued there was insufficient information to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”