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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating pollution than official data indicate, as per a new report.

Widening Gap Between Official and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on research conducted by a non-profit organization. This differs significantly with lab tests, which assumed a 75% reduction in emissions.

Analysts studied data from onboard fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the report. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in battery mode compared to overall distance. They found that just a quarter of driving was completed in EV mode, while official assumptions assumed 84%.

Additionally, when running in EV mode, pollution levels were significantly higher than official projections. This occurred because electric motors were not strong enough to function alone, resulting to combustion motors burning fossil fuels for almost a third of the travel completed in EV mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 more per year in running costs than is assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant car industries.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient information to accurately assess actual CO2 output.

“These findings show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they stated. “All regulatory changes concerning PHEVs should be made with utmost caution and in the light of that evidence.”