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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating emissions than lab-reported figures show, according to a new report.

Growing Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy organization. That differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the study. “That gap is widening and poses a significant problem. As a result, PHEVs emit almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total mileage. The team determined that only 27% of driving was completed in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission levels were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, resulting to combustion motors burning fossil fuels for almost one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

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

“The bold statements that manufacturers like to make about their PHEV cars are clearly way off the truth,” stated a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

One external energy economics expert, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the car industry argued there was too little data to properly evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert said. “All policy changes concerning PHEVs should be made with utmost caution and in the light of this data.”