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Plug-in hybrid electric vehicles produce almost five times greater planet-heating pollution than lab-reported data indicate, as per a new report.

Widening Gap In Official and Actual CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a non-profit organization. That contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are falling,” said a lead analyst participating in the report. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall distance. The team determined that just 27% of driving was completed in EV mode, whereas lab estimates suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. That happened because electric motors were not strong enough to function independently, leading to engines using gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four large automaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra annually in running costs than would be estimated under lab tests.

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been drawn back into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant car industries.

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

One independent energy economics specialist, who was not involved with the research, described the report a “highly valuable contribution” after years in which segments of the automotive industry argued there was too little data to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”