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Plug-in hybrid cars produce nearly five times more planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Widening Gap Between Official and Actual Emissions

Statistics reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a senior analyst involved in the report. “This gap is growing and creates a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode relative to overall distance. The team determined that just a quarter of travel was completed in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed four major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra per year in running expenses than would be estimated under lab tests.

“The strong claims that automakers often promote about their PHEV cars are clearly far from the truth,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought again into political debates as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with large automotive industries.

Several senior officials have suggested PHEVs as a potential “flexibility” option to include in the legislation.

An external energy economics expert, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which parts of the car sector claimed there was insufficient information to accurately evaluate actual CO2 output.

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