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Plug-in hybrid electric vehicles release nearly 5x more planet-heating emissions than official data show, as per a new report.

Widening Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit organization. That differs significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a lead analyst involved in the study. “That gap is widening and poses a significant issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of miles travelled in electric power compared to total distance. The team found that only 27% of driving was completed in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in running expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are clearly way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought back into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant car industries.

Some senior officials have suggested PHEVs as a potential “compromise” option to include in the legislation.

An external energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient data to accurately assess actual emissions.

“These findings show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of that evidence.”