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Plug-in hybrid cars release almost 5x greater planet-heating emissions than lab-reported data show, as per a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy group. That contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the report. “That discrepancy is widening and creates a serious issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to overall distance. The team determined that only a quarter of driving was completed in EV mode, whereas lab assumptions assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. This happened because electric motors were not strong enough to operate alone, leading to engines using fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more annually in operating expenses than would be estimated under lab conditions.

“The bold claims that manufacturers often promote about their PHEV cars are clearly far from the mark,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy policy specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the car industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any policy changes regarding PHEVs should be made with utmost caution and in the light of this data.”