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Plug-in hybrid electric vehicles release nearly five times more planet-heating pollution than lab-reported data indicate, as per a recent report.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit group. That contrasts sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the report. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total mileage. The team found that only 27% of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official estimates. This happened because electric motors were insufficiently powerful sufficient to function alone, leading to engines using gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four major automaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in operating costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car industries.

Several senior officials have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which segments of the car industry argued there was insufficient information to accurately evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they said. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and in the light of that data.”