Plug in Hybrid Vehicles Emit Almost as Much as Petrol Vehicles, Study Reveals

Plug-in hybrid cars produce almost five times greater planet-heating emissions than lab-reported data indicate, according to a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy organization. That contrasts sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” stated a lead researcher participating in the study. “That discrepancy is growing and poses a significant issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to total mileage. They found that only 27% of travel was done in EV mode, while official estimates assumed 84%.

Even, when running in electric mode, pollution levels were well above lab estimates. This happened because EV motors were not strong sufficient to operate alone, resulting to engines using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more per year in running costs than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid cars have recently been drawn back into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One independent energy economics specialist, who was unaffiliated with the study, described the report a “very useful addition” after years in which segments of the automotive sector argued there was too little data to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they stated. “All policy changes concerning PHEVs should be made with extreme care and in the light of this data.”