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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating pollution than official data show, according to a new analysis.

Widening Gap Between Official and Actual Emissions

Statistics reveals that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit group. This contrasts significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Analysts studied information from onboard energy use meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “That discrepancy is growing and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to overall mileage. They determined that only 27% of driving was done in EV mode, while official estimates suggested 84%.

Even, when running in electric mode, emission levels were significantly higher than lab projections. That happened because electric motors were not strong sufficient to operate alone, leading to engines burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra per year in running costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” stated a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been brought back into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant car industries.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after a long period in which parts of the car sector claimed there was too little data to properly evaluate real-world emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that data.”