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Plug-in hybrid electric vehicles produce almost 5x greater global warming emissions than official figures show, according to a new report.

Widening Gap In Official and Real-World CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit group. This differs sharply with lab estimates, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “That discrepancy is widening and creates a serious problem. As a result, PHEVs emit almost as much as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles driven in electric mode relative to overall distance. The team found that only 27% of travel was done in EV mode, while official estimates suggested over four-fifths.

Even, when running in EV mode, emission levels were well above lab projections. That occurred because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors using gasoline for almost a third of the distance covered in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled four major carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 more per year in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Political 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 targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with large car industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One external energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car industry claimed there was insufficient data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering that data.”