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Plug-in hybrid cars produce almost 5x greater planet-heating emissions than official figures show, as per a new analysis.

Growing Gap Between Official and Actual Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, according to research conducted by a non-profit group. That contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers studied data from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” stated a senior analyst involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery mode relative to overall distance. The team found that only 27% of driving was completed in EV mode, whereas official assumptions suggested 84%.

Even, when operating in electric mode, pollution amounts were well above official estimates. That occurred because EV motors were not strong sufficient to function alone, resulting to engines burning gasoline for nearly a third of the travel completed in electric mode.

Policy and Financial Implications

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

Furthermore, owners of PHEVs would pay about €500 more per year in operating expenses than would be estimated under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been brought back into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with large car industries.

Some senior politicians have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient data to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of this data.”