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PHEVs release almost 5x more planet-heating emissions than official data indicate, as per a new report.

Growing Gap Between Lab and Actual Emissions

Data reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy group. That contrasts sharply with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a senior researcher involved in the study. “That gap is widening and creates a significant problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in battery mode compared to overall distance. They determined that just 27% of driving was completed in electric mode, while lab estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output enabled several major carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend about €500 extra annually in running expenses than is assumed under lab tests.

“The bold claims that manufacturers often promote about their PHEV cars are clearly way off the mark,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from member states with significant automotive manufacturing.

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

One independent energy economics expert, who was not involved with the research, described the report a “highly valuable contribution” after years in which parts of the automotive industry claimed there was too little data to accurately assess actual emissions.

“These findings show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be made with utmost care and considering that evidence.”