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Plug-in hybrid electric vehicles emit almost five times greater planet-heating pollution than official data indicate, as per a recent report.

Widening Discrepancy In Official and Real-World Emissions

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit group. That contrasts sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the report. “That gap is widening and creates a serious issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric power relative to total mileage. The team found that only a quarter of driving was completed in electric mode, while lab estimates assumed over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. This happened because EV motors were insufficiently powerful enough to function independently, leading to engines using gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled several large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

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

“The bold statements that automakers like to make about their PHEV cars are clearly far from the mark,” stated a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large automotive industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which parts of the automotive industry argued there was insufficient information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert stated. “Any regulatory changes regarding PHEVs should be implemented with extreme care and considering this data.”