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Plug-in hybrid electric vehicles emit nearly five times more planet-heating pollution than lab-reported figures show, according to a new report.

Widening Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy group. This differs sharply with lab tests, which suggested a 75% reduction in pollution.

Analysts studied information from onboard energy use meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a senior analyst involved in the study. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs emit almost as much as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to overall distance. The team found that just 27% of travel was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, emission levels were significantly higher than lab projections. That occurred because EV motors were not strong enough to function alone, resulting to combustion motors burning fossil fuels for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed several major carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been brought back into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban 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 senior officials have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

An independent energy economics expert, who was not involved with the research, described the report a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient information to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” they stated. “Any policy changes regarding PHEVs should be implemented with utmost caution and in the light of that data.”