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Plug-in hybrid cars produce almost five times more planet-heating pollution than lab-reported figures show, as per a recent report.

Widening Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, based on analysis conducted by a non-profit organization. That contrasts significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” said a lead researcher participating in the study. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in battery power relative to overall distance. They determined that just a quarter of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when running in electric mode, pollution amounts were well above lab projections. That happened because electric motors were not strong sufficient to function alone, leading to engines using fossil fuels for almost one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in running expenses than is assumed under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid cars have lately been drawn back into political debates as automakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the car industry argued there was insufficient data to properly evaluate real-world emissions.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” they said. “Any policy adjustments concerning PHEVs should be made with utmost caution and considering this data.”