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Plug-in hybrid cars emit nearly five times greater planet-heating emissions than official data indicate, as per a new analysis.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a non-profit organization. That differs significantly with laboratory estimates, which suggested a 75% decrease in emissions.

Analysts studied information from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a senior researcher involved in the study. “That discrepancy is growing and poses a significant issue. As a result, PHEVs emit nearly as much as petrol cars.”

Key Factors Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery mode relative to overall distance. They found that only 27% of travel was completed in electric mode, while official assumptions assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above official estimates. That happened because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors using fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The strong claims that automakers like to make about their PHEV cars are obviously far from the mark,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with large automotive industries.

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

An external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after a long period in which segments of the automotive sector claimed there was insufficient data to accurately assess actual emissions.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”