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PHEVs emit almost five times greater planet-heating pollution than official data show, as per a recent analysis.

Growing Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit group. That contrasts sharply with laboratory estimates, which suggested a 75% decrease in pollution.

Analysts examined information from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a senior researcher participating in the study. “This gap is widening and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to overall distance. They determined that just a quarter of driving was done in electric mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab projections. This occurred because electric motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in running costs than would be estimated under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have lately been brought again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which parts of the car industry argued there was insufficient information to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” they said. “Any regulatory changes concerning PHEVs should be implemented with extreme care and considering this evidence.”