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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating emissions than lab-reported data indicate, according to a recent analysis.

Growing Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit organization. That differs sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold 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 estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode compared to overall mileage. The team found that only a quarter of driving was done in EV mode, whereas official estimates assumed 84%.

Even, when running in EV mode, emission levels were well above lab projections. This occurred because electric motors were insufficiently powerful enough to function alone, leading to combustion motors burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into policy discussions as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with significant automotive industries.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One independent energy economics expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which parts of the car industry argued there was insufficient data to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” the expert said. “All policy changes concerning PHEVs should be made with extreme caution and considering this evidence.”