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Plug-in hybrid cars emit almost five times greater global warming pollution than official data show, as per a new analysis.

Widening Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit organization. This contrasts significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Analysts examined data from onboard energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” stated a senior analyst participating in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in battery power relative to overall mileage. The team found that just a quarter of driving was done in electric mode, while official assumptions suggested 84%.

Even, when running in EV mode, emission levels were significantly higher than official estimates. This occurred because EV motors were not strong sufficient to operate independently, leading to combustion motors using fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more annually in running expenses than is estimated under lab tests.

“The strong statements that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have lately been brought back into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

An external energy economics specialist, who was unaffiliated with the study, called the analysis a “highly valuable addition” after years in which parts of the car sector argued there was too little information to accurately assess real-world CO2 output.

“These findings show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “All policy changes concerning PHEVs should be implemented with utmost care and in the light of that data.”