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Plug-in hybrid cars release almost five times greater planet-heating emissions than official data indicate, according to a recent report.

Growing Gap In Lab and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit group. This differs significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total distance. They found that only 27% of driving was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab projections. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra annually in running costs than would be assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant car manufacturing.

Some high-level officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive industry claimed there was too little information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they stated. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”