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Plug-in hybrid electric vehicles produce almost five times more planet-heating pollution than lab-reported data show, according to a recent analysis.

Growing Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy group. This contrasts significantly with lab tests, which suggested a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a lead analyst involved in the study. “That gap is widening and creates a significant problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to total mileage. They determined that only a quarter of travel was done in electric mode, while official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate independently, resulting to engines using fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more per year in running expenses than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which segments of the automotive industry claimed there was insufficient data to properly assess actual CO2 output.

“The results demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” they stated. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this evidence.”