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Plug-in hybrid electric vehicles release nearly 5x greater planet-heating emissions than lab-reported data indicate, as per a recent report.

Widening Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy organization. This differs significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts studied data from onboard fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a lead analyst participating in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to overall mileage. They determined that just 27% of driving was done in EV mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab projections. That happened because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning fossil fuels for almost a third of the distance covered in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in operating expenses than is assumed under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car manufacturing.

Several high-level officials have suggested PHEVs as a possible “compromise” solution to include in the legislation.

An independent energy policy expert, who was not involved with the study, called the report a “highly valuable contribution” after years in which segments of the automotive industry argued there was insufficient information to properly evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with utmost care and in the light of that data.”