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Plug-in hybrid electric vehicles release almost 5x more planet-heating emissions than lab-reported data indicate, according to a recent analysis.

Growing Gap In Official and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a advocacy group. That contrasts significantly with lab estimates, which suggested a 75% decrease in emissions.

Analysts studied information from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are falling,” stated a senior researcher involved in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

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

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate independently, leading to combustion motors burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four large automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more annually in running expenses than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive manufacturing.

Several senior politicians have proposed PHEVs as a possible “compromise” solution to include in the regulation.

One external energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which segments of the car sector claimed there was insufficient information to properly assess real-world CO2 output.

“These findings show, without question, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and considering this data.”