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Plug-in hybrid cars emit almost five times greater global warming pollution than official figures indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a advocacy group. That contrasts sharply with laboratory estimates, which suggested a 75% decrease in emissions.

Researchers studied information from onboard fuel consumption monitors of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior researcher involved in the report. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to overall distance. They found that just 27% of travel was completed in EV mode, whereas official estimates assumed over four-fifths.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using gasoline for almost one-third of the travel completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed several major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly far from the mark,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into political debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

An external energy policy specialist, who was not involved with the study, called the report a “highly valuable contribution” after years in which parts of the automotive industry claimed there was too little data to accurately assess actual CO2 output.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost care and considering this data.”