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Plug-in hybrid cars release nearly five times greater planet-heating pollution than lab-reported figures indicate, according to a new report.

Widening Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy organization. This differs sharply with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand cars 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 official estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric power relative to overall distance. They found that just 27% of driving was completed in EV mode, while lab estimates suggested 84%.

Even, when operating in electric mode, emission levels were significantly higher than lab estimates. That happened because electric motors were not strong enough to function alone, resulting to engines burning gasoline for nearly a third of the distance completed in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled several large automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more per year in operating costs than is assumed under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have lately been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant car manufacturing.

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

An independent energy economics expert, who was not involved with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient data to properly assess real-world CO2 output.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they said. “All policy changes concerning PHEVs should be made with extreme caution and in the light of this data.”