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PHEVs produce nearly 5x greater global warming emissions than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy organization. This contrasts sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead researcher involved in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles driven in electric power compared to total mileage. The team found that only 27% of driving was done in electric mode, while official assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab projections. This occurred because EV motors were not strong enough to function independently, leading to engines using gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV emissions enabled four large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more annually in running costs than would be estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought again into political debates as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with large automotive industries.

Several senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One independent energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the car sector argued there was too little information to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”