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PHEVs emit nearly five times more planet-heating emissions than official figures indicate, according to a recent report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “That discrepancy is growing and poses a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total mileage. They found that only 27% of travel was completed in EV mode, whereas lab assumptions assumed 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than official estimates. That occurred because EV motors were not strong enough to function independently, resulting to engines burning fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 more annually in operating costs than is estimated under lab tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn again into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from member states with large automotive industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the legislation.

An independent energy economics expert, who was not involved with the research, described the report a “very useful addition” after a long period in which segments of the automotive industry argued there was too little data to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be implemented with utmost caution and in the light of that data.”