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PHEVs produce nearly five times greater global warming pollution than official figures show, according to a new analysis.

Widening Discrepancy In Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a senior researcher involved in the report. “This discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles driven in electric power compared to overall distance. They found that only 27% of driving was completed in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official projections. That happened because electric motors were insufficiently powerful enough to function alone, resulting to engines using gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ standards.

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

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car industries.

Some senior officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

An external energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after a long period in which parts of the car industry claimed there was insufficient information to properly evaluate actual CO2 output.

“The results show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they said. “Any policy changes concerning PHEVs should be made with extreme care and in the light of that data.”