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Plug-in hybrid cars release nearly five times more planet-heating emissions than official data show, according to a recent report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy group. This contrasts sharply with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior analyst participating in the study. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. They found that just 27% of driving was completed in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, pollution levels were significantly higher than lab projections. This happened because electric motors were not strong sufficient to function independently, leading to combustion motors using fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed several large automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in operating expenses than is estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from member states with significant car industries.

Several high-level officials have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

One external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable addition” after years in which segments of the automotive industry claimed there was insufficient data to properly assess real-world emissions.

“The results show, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be made with extreme care and considering this data.”