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PHEVs release nearly 5x more global warming pollution than official data show, as per a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with laboratory tests, which suggested a 75% decrease in emissions.

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

“Actual CO2 output are increasing, while official emissions are falling,” stated a senior analyst involved in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery mode compared to total distance. The team found that just a quarter of driving was done in electric mode, while lab estimates assumed over four-fifths.

Even, when running in electric mode, emission levels were well above lab projections. This happened because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four major automaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more per year in running costs than would be estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into political discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from member states with significant automotive industries.

Several senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

An external energy economics expert, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “All policy changes regarding PHEVs should be implemented with extreme caution and considering that data.”