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Plug-in hybrid electric vehicles produce almost 5x more global warming pollution than official figures show, as per a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy organization. That differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead researcher involved in the report. “This discrepancy is growing and creates a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of miles driven in electric mode compared to overall mileage. They found that only 27% of driving was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to function independently, leading to engines burning fossil fuels for almost a third of the distance completed in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

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

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

One external energy economics expert, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the car industry argued there was too little data to properly assess actual emissions.

“The results demonstrate, without question, that the gap in lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” the expert said. “Any policy changes regarding PHEVs should be implemented with utmost care and considering that evidence.”