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Plug-in hybrid cars emit almost five times greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Widening Gap Between Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. That differs significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” stated a senior analyst participating in the study. “This gap is widening and creates a significant problem. Consequently, PHEVs emit almost 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 miles driven in battery power relative to total mileage. The team determined that just a quarter of driving was done in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than official estimates. This happened because EV motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong claims that manufacturers like to make about their PHEV vehicles are clearly far from the mark,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant automotive industries.

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

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was too little information to properly evaluate actual CO2 output.

“The results show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be implemented with extreme caution and considering this data.”