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Plug-in hybrid cars produce almost 5x more planet-heating pollution than official data show, according to a recent report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts significantly with laboratory tests, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a senior researcher involved in the report. “That gap is widening and poses a significant issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall distance. The team found that just 27% of driving was done in electric mode, whereas official assumptions assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning gasoline for nearly a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra annually in running expenses than would be estimated under lab tests.

“The strong claims that automakers like to make about their PHEV cars are clearly far from the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting 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 expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient data to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”