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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating emissions than official figures show, as per a recent report.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. This contrasts significantly with lab tests, which assumed a three-quarters reduction in emissions.

Researchers examined information from onboard energy use meters of 800,000 cars sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” said a lead researcher participating in the study. “That gap is growing and creates a significant problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to overall mileage. They determined that just 27% of travel was done in EV mode, while official assumptions suggested 84%.

Even, when operating in EV mode, emission levels were significantly higher than official projections. That occurred because electric motors were insufficiently powerful enough to function alone, leading to engines using fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed four major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more per year in running costs than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought back into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” option to include in the regulation.

One external energy policy expert, who was not involved with the research, called the report a “highly valuable contribution” after years in which segments of the car sector argued there was insufficient data to properly evaluate real-world emissions.

“The results show, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be made with extreme care and considering that data.”