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PHEVs emit almost five times greater planet-heating pollution than lab-reported figures show, as per a recent report.

Widening Gap Between Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy group. That contrasts significantly with laboratory tests, which suggested a 75% decrease in emissions.

Researchers studied data from in-vehicle energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “This discrepancy is growing and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Behind the Discrepancy

Analysts linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall mileage. They determined that just 27% of travel was done in electric mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to engines burning gasoline for nearly one-third of the travel covered in EV mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra annually in running costs than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have proposed PHEVs as a possible “compromise” solution to include in the legislation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive sector argued there was too little data to properly evaluate real-world CO2 output.

“These findings show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they said. “All regulatory adjustments regarding PHEVs should be made with extreme caution and in the light of this data.”