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Plug-in hybrid cars release almost five times more planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That contrasts sharply with lab tests, which suggested a 75% decrease in pollution.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a senior analyst involved in the study. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles driven in battery mode relative to overall distance. The team found that only 27% of driving was done in EV mode, whereas official assumptions suggested 84%.

Even, when operating in EV mode, pollution amounts were well above official estimates. This occurred because electric motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for almost a third of the travel completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 more annually in running costs than would be assumed under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into political debates as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with significant automotive industries.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

One independent energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car industry claimed there was insufficient data to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be made with extreme care and in the light of this evidence.”