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Plug-in hybrid electric vehicles emit almost 5x more planet-heating emissions than official figures indicate, as per a recent analysis.

Widening Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit group. That differs sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a senior analyst participating in the report. “That gap is widening and poses a serious issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to total mileage. They determined that only a quarter of travel was completed in electric mode, while official assumptions suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were not strong enough to operate alone, leading to combustion motors using fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 extra per year in operating costs than is assumed under lab conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have lately been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car industries.

Several senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

One independent energy economics expert, who was not involved with the study, described the analysis a “very useful addition” after a long period in which parts of the automotive industry claimed there was too little information to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be implemented with utmost care and in the light of that evidence.”