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Plug-in hybrid cars produce almost 5x greater planet-heating emissions than official figures indicate, according to a recent report.

Widening Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit group. That differs sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” stated a senior analyst involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total mileage. The team found that only a quarter of travel was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were well above official projections. That happened because electric motors were not strong enough to operate independently, leading to engines burning fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in running costs than is assumed under laboratory tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into policy debates as carmakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large car manufacturing.

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One external energy economics expert, who was not involved with the study, described the report a “highly valuable addition” after years in which segments of the car industry claimed there was too little information to properly evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional cars,” the expert said. “All policy changes regarding PHEVs should be made with extreme caution and considering this evidence.”