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

Widening Gap In Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research conducted by a non-profit organization. This differs significantly with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a lead analyst involved in the report. “That discrepancy is widening and creates a serious issue. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to total distance. They determined that just a quarter of driving was done in EV mode, while lab estimates assumed 84%.

Even, when running in electric mode, pollution amounts were significantly higher than official projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to combustion motors using fossil fuels for nearly a third of the distance covered in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more annually in running costs than would be assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from member states with significant automotive industries.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

An external energy economics expert, who was not involved with the research, described the report a “very useful addition” after a long period in which parts of the automotive sector claimed there was too little data to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert said. “Any policy changes concerning PHEVs should be made with extreme caution and in the light of this data.”