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PHEVs release almost five times greater planet-heating pollution than official figures show, according to a recent analysis.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy organization. This contrasts sharply with lab estimates, which suggested a 75% reduction in emissions.

Analysts examined data from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a lead researcher participating in the report. “That discrepancy is widening and creates a serious issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric mode relative to total distance. They determined that just a quarter of driving was done in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than official projections. That occurred because electric motors were not strong enough to function independently, leading to engines burning gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 more per year in running expenses than is estimated under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from member states with significant automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” option to include in the legislation.

One external energy policy specialist, who was not involved with the study, described the report a “very useful contribution” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”