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Plug-in hybrid cars emit almost five times more planet-heating pollution than lab-reported figures indicate, according to a recent report.

Growing Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit organization. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a senior analyst participating in the report. “This gap is growing and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in electric power compared to overall distance. The team determined that only 27% of travel was completed in EV mode, while lab estimates assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above official projections. This happened because EV motors were not strong enough to function independently, resulting to engines using gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled several large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more per year in operating expenses than is assumed under laboratory conditions.

“The strong claims that automakers like to make about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been brought back into policy discussions as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and opposition from member states with significant car manufacturing.

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

One external energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car industry claimed there was insufficient data to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with extreme care and considering this evidence.”