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PHEVs produce nearly 5x greater global warming emissions than lab-reported data show, as per a new report.

Widening Gap Between Official and Real-World Emissions

Data shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. That contrasts significantly with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a senior researcher participating in the report. “This gap is growing and creates a serious problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric power relative to total distance. The team found that only a quarter of travel was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were well above official estimates. This happened because electric motors were insufficiently powerful sufficient to function alone, resulting to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output enabled several major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running expenses than is assumed under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have lately been brought back into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with significant car industries.

Some high-level officials have suggested PHEVs as a potential “flexibility” solution to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the research, described the report a “very useful addition” after years in which parts of the car sector argued there was insufficient information to properly evaluate actual emissions.

“The results demonstrate, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”