Plug-in Hybrid Vehicles Pollute Almost as Heavily as Petrol Vehicles, Report Reveals

PHEVs produce nearly 5x more global warming emissions than lab-reported figures show, according to a new report.

Widening Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs emit just 19% less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a advocacy organization. This differs significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a senior analyst participating in the study. “This gap is widening and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric power relative to overall mileage. They found that only 27% of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Even, when running in electric mode, pollution amounts were well above lab projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more annually in operating expenses than would be assumed under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously far from the mark,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the study, described the analysis a “very useful contribution” after a long period in which segments of the car industry argued there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”