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PHEVs produce almost 5x more planet-heating pollution than lab-reported data show, according to a new report.

Growing Gap In Official and Actual CO2 Output

Data shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a advocacy organization. That differs significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers studied data from onboard energy use meters of 800,000 cars registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “That discrepancy is growing and poses a serious issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to total mileage. The team determined that just 27% of driving was done in electric mode, while lab assumptions assumed 84%.

Even, when operating in electric mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 more annually in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into political debates as carmakers 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 significant automotive manufacturing.

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

One independent energy economics expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the car industry claimed there was too little data to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” they stated. “Any regulatory changes regarding PHEVs should be implemented with extreme care and considering that data.”