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PHEVs produce nearly 5x more planet-heating emissions than official figures indicate, according to a recent report.

Widening Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy organization. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts examined information from onboard energy use meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” said a senior analyst participating in the study. “That gap is widening and poses a significant issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall mileage. The team found that just a quarter of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than lab projections. This happened because electric motors were insufficiently powerful enough to function alone, leading to combustion motors using fossil fuels for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more annually in running costs than would be assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large automotive industries.

Several senior politicians have proposed PHEVs as a possible “flexibility” option to include in the regulation.

One external energy economics expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive sector argued there was too little information to accurately assess real-world emissions.

“These findings show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”