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Plug-in hybrid cars release nearly 5x more planet-heating pollution than lab-reported data indicate, as per a recent report.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy group. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts studied data from onboard energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior researcher participating in the report. “This discrepancy is widening and poses a significant issue. As a result, PHEVs pollute almost as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. They determined that only 27% of driving was done in EV mode, while official estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. This happened because electric motors were not strong enough to function independently, resulting to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating expenses than is estimated under lab conditions.

“The strong claims that manufacturers often promote about their PHEV cars are clearly far from the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought back into policy debates as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with significant automotive industries.

Several senior officials have proposed PHEVs as a potential “compromise” option to include in the legislation.

An external energy policy specialist, who was not involved with the study, described the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient data to accurately assess real-world emissions.

“These findings show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and considering this data.”