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Plug-in hybrid cars produce almost five times greater planet-heating pollution than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. This contrasts sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead researcher participating in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric power compared to total mileage. They found that just 27% of driving was done in EV mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running costs than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large car manufacturing.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which parts of the car sector claimed there was too little information to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “Any policy changes concerning PHEVs should be made with extreme care and considering that data.”