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Plug-in hybrid cars produce nearly 5x more planet-heating pollution than lab-reported data show, according to a recent report.

Widening Gap In Official and Real-World Emissions

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts sharply with lab estimates, which assumed a 75% decrease in emissions.

Researchers studied information from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the study. “That discrepancy is widening and poses a significant issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. They found that just a quarter of travel was done in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in EV mode, pollution amounts were well above official estimates. That happened because electric motors were not strong sufficient to function alone, leading to engines burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in running costs than is estimated under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid cars have recently been brought again into political debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

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

An external energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” they said. “All regulatory changes regarding PHEVs should be made with utmost caution and in the light of that data.”