🔗 Share this article

Plug-in hybrid cars release nearly 5x more planet-heating pollution than lab-reported figures indicate, according to a recent analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit group. That contrasts sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” stated a senior researcher participating in the report. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to total mileage. The team determined that just a quarter of travel was completed in electric mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than lab estimates. That happened because EV motors were not strong enough to operate alone, leading to engines burning fossil fuels for nearly one-third of the travel completed in electric mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV CO2 output enabled several large automaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra per year in running expenses than would be estimated under lab conditions.

“The bold claims that automakers like to make about their PHEV vehicles are clearly way off the truth,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with large car manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the car industry argued there was insufficient information to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” they stated. “Any regulatory changes concerning PHEVs should be implemented with utmost care and in the light of that evidence.”