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Plug-in hybrid electric vehicles produce almost 5x more planet-heating emissions than official data show, according to a recent analysis.

Growing Gap In Official and Real-World Emissions

Data shows that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit group. This differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” said a senior researcher participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total distance. They found that just 27% of driving was completed in EV mode, while lab assumptions assumed over four-fifths.

Even, when running in EV mode, pollution amounts were well above lab estimates. That happened because electric motors were not strong sufficient to function independently, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV emissions allowed several large carmaker groups to escape over €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay about €500 extra annually in operating expenses than would be assumed under lab tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been brought back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after a long period in which parts of the car industry claimed there was insufficient data to properly evaluate actual emissions.

“These findings demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be made with utmost caution and considering that evidence.”