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Plug-in hybrid electric vehicles release almost five times more planet-heating emissions than official figures indicate, according to a new report.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official figures are decreasing,” said a lead researcher participating in the report. “That discrepancy is growing and creates a serious issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery power compared to total distance. They determined that just a quarter of driving was done in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were significantly higher than official projections. This occurred because EV motors were not strong sufficient to function alone, resulting to engines using gasoline for nearly a third of the travel completed in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV emissions enabled four large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running expenses than is estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn back into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive manufacturing.

Some high-level officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

One external energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the car sector argued there was insufficient information to properly assess actual emissions.

“The results show, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they stated. “All policy changes concerning PHEVs should be made with extreme care and in the light of that evidence.”