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Plug-in hybrid cars emit almost 5x more planet-heating pollution than lab-reported figures indicate, as per a new analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. This contrasts sharply with laboratory tests, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the report. “That discrepancy is growing and creates a significant issue. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. They determined that just a quarter of driving was done in electric mode, while official estimates assumed over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to function alone, resulting to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four major carmaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

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

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn again into political discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large car industries.

Some senior officials have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

An independent energy economics expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the car sector argued there was insufficient data to accurately evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that data.”