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PHEVs release nearly 5x greater planet-heating pollution than lab-reported data show, according to a recent report.

Growing Gap Between Lab and Real-World Emissions

Data reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit group. That differs significantly with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers examined data from in-vehicle energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” said a lead analyst involved in the study. “That gap is widening and poses a significant problem. As a result, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode compared to overall distance. They determined that just 27% of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official projections. That occurred because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several major carmaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 more per year in operating costs than would be estimated under lab tests.

“The bold statements that automakers like to make about their PHEV vehicles are clearly far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large car manufacturing.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An independent energy policy specialist, who was not involved with the research, described the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with utmost caution and in the light of this data.”