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PHEVs emit nearly 5x more planet-heating pollution than lab-reported data indicate, according to a recent report.

Growing Gap Between Official and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a non-profit group. That contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” said a senior researcher involved in the report. “This gap is growing and creates a significant problem. As a result, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total mileage. They found that just a quarter of driving was done in electric mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission levels were well above official projections. This happened because electric motors were not strong sufficient to operate alone, resulting to engines using fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in running costs than is assumed under lab conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are obviously far from the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought back into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant automotive industries.

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

One external energy policy expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was insufficient data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme care and considering that evidence.”