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PHEVs release almost five times more planet-heating pollution than lab-reported figures show, according to a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on research carried out by a advocacy organization. That contrasts significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a lead analyst participating in the report. “This gap is growing and creates a significant issue. As a result, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall distance. The team found that only a quarter of driving was completed in electric mode, whereas lab estimates assumed 84%.

Even, when running in electric mode, pollution levels were well above lab estimates. This happened because electric motors were not strong sufficient to operate alone, resulting to engines using gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions allowed several major automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more annually in operating expenses than is assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Hybrid cars have lately been brought back into political debates as carmakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car industries.

Some high-level politicians have suggested plug-in hybrids as a possible “compromise” option to include in the regulation.

One external energy policy expert, who was not involved with the research, described the report a “very useful contribution” after years in which parts of the automotive sector claimed there was too little information to properly assess real-world emissions.

“These findings demonstrate, without question, that the gap in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they said. “All policy changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”