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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy organization. This contrasts sharply with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a lead researcher participating in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total mileage. They determined that just a quarter of driving was done in electric mode, while lab assumptions suggested 84%.

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

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed several major automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra annually in operating costs than is estimated under lab tests.

“The bold claims that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn back into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Several high-level politicians have suggested PHEVs as a potential “flexibility” option to include in the regulation.

An external energy economics expert, who was not involved with the research, called the report a “very useful contribution” after a long period in which segments of the car sector claimed there was too little data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be made with extreme care and in the light of that evidence.”