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Plug-in hybrid electric vehicles emit almost five times more planet-heating emissions than lab-reported data show, as per a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research carried out by a advocacy group. This differs sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” stated a lead researcher participating in the report. “That gap is widening and poses a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles driven in battery power compared to overall mileage. They determined that only a quarter of travel was completed in EV mode, whereas official estimates suggested 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab projections. That happened because electric motors were insufficiently powerful enough to function alone, leading to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV emissions allowed several major automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 more annually in operating expenses than would be estimated under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant automotive industries.

Some senior politicians have proposed PHEVs as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was insufficient data to properly assess real-world emissions.

“The results show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that evidence.”