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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy organization. That contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the study. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs emit almost as much as gasoline cars.”

Key Factors Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to overall distance. They determined that only a quarter of driving was done in EV mode, while lab estimates suggested over four-fifths.

Even, when running in electric mode, emission amounts were well above lab projections. That occurred because electric motors were not strong enough to function independently, leading to engines burning gasoline for almost one-third of the travel covered in electric mode.

Policy and Financial Consequences

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

Furthermore, drivers of PHEVs could pay about €500 more per year in running expenses than is assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Hybrid cars have lately been drawn back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

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

One external energy economics specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” they said. “All policy adjustments regarding PHEVs should be implemented with utmost care and in the light of that evidence.”