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

Growing Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy group. This differs sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” said a senior analyst involved in the report. “That gap is widening and creates a serious problem. As a result, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total distance. They determined that just 27% of travel was completed in EV mode, while lab estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This occurred because electric motors were not strong enough to function alone, resulting to combustion motors using gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output enabled several large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more annually in running expenses than is estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been drawn again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive industries.

Some high-level politicians have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive sector claimed there was insufficient data to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering that evidence.”