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Plug-in hybrid electric vehicles produce nearly five times greater global warming pollution than official data indicate, according to a new analysis.

Widening Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit organization. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined information from onboard energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” stated a senior researcher involved in the study. “That gap is widening and poses a serious issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to overall distance. They found that just a quarter of driving was done in electric mode, while official estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab projections. That occurred because EV motors were not strong enough to operate alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled four large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 more per year in running expenses than is assumed under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy discussions as automakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive industries.

Some senior politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which parts of the car sector claimed there was insufficient data to properly assess actual CO2 output.

“The results show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they said. “Any policy changes concerning PHEVs should be made with extreme caution and considering this data.”