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Plug-in hybrid cars release nearly 5x greater global warming pollution than lab-reported data show, according to a recent analysis.

Widening Gap In Official and Actual CO2 Output

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy organization. That contrasts sharply with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a senior researcher participating in the study. “That discrepancy is widening and poses a serious issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power relative to total distance. The team found that just 27% of driving was done in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate independently, resulting to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more per year in running expenses than would be estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large automotive industries.

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

An external energy policy expert, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which parts of the automotive sector argued there was insufficient information to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of this data.”