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PHEVs emit nearly five times greater planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Growing Gap Between Lab and Actual Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, according to analysis conducted by a advocacy group. That contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers studied information from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This discrepancy is widening and creates a significant issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery power relative to overall mileage. The team found that just a quarter of driving was completed in EV mode, whereas lab assumptions assumed 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than official estimates. This occurred because electric motors were not strong enough to function alone, leading to combustion motors using fossil fuels for almost a third of the distance covered in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions enabled several large automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra per year in operating costs than is estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are obviously way off the mark,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car industries.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after a long period in which segments of the automotive industry argued there was insufficient data to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and considering this data.”