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Plug-in hybrid electric vehicles emit nearly five times more planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, based on research carried out by a advocacy organization. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the study. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in battery power compared to overall distance. They determined that just a quarter of driving was done in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in electric mode, emission amounts were well above official estimates. This occurred because EV motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning fossil fuels for almost one-third of the travel covered in electric mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 more annually in running costs than is assumed under laboratory conditions.

“The bold statements that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car industries.

Some senior officials have proposed plug-in hybrids as a possible “compromise” solution to include in the regulation.

An independent energy policy expert, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the automotive sector argued there was too little information to properly evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” they stated. “All policy changes regarding PHEVs should be made with extreme care and in the light of that data.”