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PHEVs emit nearly 5x more planet-heating pollution than official data indicate, according to a new report.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from onboard fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a senior researcher participating in the report. “This discrepancy is widening and creates a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall distance. They found that just 27% of travel was done in electric mode, while lab assumptions suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. That occurred because EV motors were insufficiently powerful enough to function alone, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 extra per year in operating expenses than would be estimated under lab conditions.

“The bold claims that manufacturers often promote about their PHEV cars are obviously way off the truth,” stated a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have lately been brought back into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

Some high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which parts of the car industry argued there was insufficient information to properly evaluate real-world emissions.

“The results show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel cars,” they said. “All regulatory changes regarding PHEVs should be implemented with utmost care and considering that data.”