🔗 Share this article

Plug-in hybrid electric vehicles produce nearly five times greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy organization. This differs significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the study. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in battery power compared to total mileage. They found that just 27% of driving was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above lab estimates. That happened because EV motors were insufficiently powerful sufficient to function independently, resulting 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 underestimation of PHEV emissions allowed several major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 more per year in running costs than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large car industries.

Several senior officials have suggested PHEVs as a possible “compromise” option to include in the regulation.

An external energy policy expert, who was not involved with the study, described the analysis a “very useful contribution” after years in which segments of the automotive sector claimed there was too little data to properly assess actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost caution and considering this evidence.”