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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than lab-reported data indicate, according to a recent analysis.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. That differs significantly with laboratory tests, which suggested a 75% reduction in emissions.

Researchers examined information from onboard energy use meters 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 nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a lead analyst involved in the report. “That gap is growing and creates a significant problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to overall distance. The team found that only 27% of driving was completed in electric mode, while lab estimates assumed 84%.

Additionally, when running in EV mode, emission levels were significantly higher than official estimates. That happened 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 EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four major carmaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra annually in running costs than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with large car industries.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which segments of the car sector claimed there was too little information to properly evaluate real-world emissions.

“The results show, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they stated. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of this data.”