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Plug-in hybrid electric vehicles produce almost five times greater planet-heating emissions than official data show, as per a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel cars, according to research carried out by a advocacy organization. That differs significantly with laboratory tests, which suggested a 75% decrease in pollution.

Researchers studied information from onboard energy use monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a senior analyst participating in the report. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall distance. They found that just a quarter of driving was completed in EV mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to operate independently, resulting to engines burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 extra per year in operating costs than would be assumed under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn again into policy debates as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car manufacturing.

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

An external energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was insufficient information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” they stated. “All regulatory changes regarding PHEVs should be made with utmost caution and considering that data.”