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PHEVs release almost 5x more planet-heating emissions than lab-reported figures show, according to a new report.

Widening Gap Between Lab and Actual Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a advocacy group. That contrasts significantly with laboratory tests, which assumed a 75% reduction in pollution.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” said a lead analyst participating in the report. “This gap is widening and poses a significant problem. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power relative to total mileage. They determined that only 27% of travel was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when running in EV mode, emission levels were significantly higher than official projections. That happened because EV motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for almost a third of the travel completed in EV mode.

Policy and Financial Consequences

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

Furthermore, owners of PHEVs would spend about €500 extra annually in running costs than is assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into political debates as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Several senior politicians have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

One external energy economics specialist, who was unaffiliated with the study, described the report a “very useful addition” after years in which parts of the automotive industry claimed there was too little information to properly assess real-world CO2 output.

“The results show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and considering this evidence.”