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PHEVs release almost 5x greater planet-heating emissions than official figures show, according to a new analysis.

Growing Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy group. This differs sharply with laboratory tests, which assumed a 75% decrease in emissions.

Researchers studied information from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead researcher participating in the report. “That discrepancy is growing and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to total mileage. They determined that just a quarter of driving was done in EV mode, whereas official assumptions suggested over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than lab estimates. This happened because electric motors were not strong sufficient to function alone, leading to combustion motors using gasoline for almost one-third of the travel completed in EV mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions allowed four large automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend about €500 more annually in operating costs than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car industries.

Some high-level officials have proposed PHEVs as a possible “compromise” option to include in the regulation.

An external energy economics expert, who was not involved with the research, called the analysis a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little information to accurately assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” they said. “Any regulatory changes concerning PHEVs should be made with extreme caution and in the light of this evidence.”