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Plug-in hybrid cars produce nearly five times more global warming emissions than lab-reported figures show, as per a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit group. This differs significantly with lab tests, which suggested a three-quarters decrease in emissions.

Analysts examined information from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a lead researcher participating in the report. “That gap is widening and poses a serious issue. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall distance. They determined that just a quarter of driving was done in EV mode, whereas lab estimates suggested 84%.

Even, when running in EV mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were not strong sufficient to function independently, leading to combustion motors using fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV emissions allowed several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 extra annually in running costs than is estimated under laboratory conditions.

“The bold claims that automakers often promote about their PHEV vehicles are clearly far from the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive industries.

Some senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

One external energy economics specialist, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which parts of the car industry argued there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they stated. “Any policy changes regarding PHEVs should be implemented with utmost care and considering this data.”