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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than official figures show, according to a recent report.

Growing Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit group. This differs sharply with laboratory estimates, which suggested a three-quarters reduction in emissions.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” stated a senior researcher participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to overall mileage. They determined that only a quarter of driving was completed in EV mode, while official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled four major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in running costs than would be assumed under laboratory conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with significant automotive manufacturing.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, described the report a “highly valuable addition” after a long period in which parts of the car sector claimed there was insufficient information to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”