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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than official figures show, according to a recent report.

Widening Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy group. That differs significantly with lab tests, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use meters of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior researcher participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric mode compared to total mileage. The team determined that only 27% of travel was done in EV mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were not strong sufficient to operate alone, leading to engines using gasoline for almost a third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled four major carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra per year in running expenses than would be estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into political debates as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large automotive industries.

Several high-level officials have suggested PHEVs as a potential “flexibility” option to introduce in the legislation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was insufficient data to properly evaluate actual emissions.

“The results show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost caution and considering that evidence.”