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Plug-in hybrid cars release nearly 5x greater global warming emissions than official data show, according to a new analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. This differs sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied information from in-vehicle energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a lead analyst participating in the report. “This discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to total distance. The team found that just 27% of driving was done in electric mode, whereas lab estimates suggested 84%.

Even, when operating in electric mode, emission amounts were significantly higher than official estimates. This happened because electric motors were not strong enough to operate alone, leading to engines burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled four large automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong claims that automakers often promote about their plug-in hybrid 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 environment and saving money. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have pressed the European Union to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

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

One independent energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they said. “Any policy changes concerning PHEVs should be made with extreme caution and considering that evidence.”