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Plug-in hybrid electric vehicles release nearly 5x more planet-heating pollution than lab-reported data show, as per a new report.

Growing Gap In Lab and Real-World Emissions

Data shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, according to research conducted by a non-profit group. This contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a lead researcher involved in the study. “This gap is widening and creates a significant issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery mode compared to overall distance. They determined that just a quarter of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using fossil fuels for almost a third of the travel covered in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running expenses than would be assumed under laboratory tests.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the truth,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into political debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large automotive industries.

Several senior politicians have suggested plug-in hybrids as a possible “compromise” option to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive sector argued there was insufficient data to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they said. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and in the light of that evidence.”