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Plug-in hybrid electric vehicles emit nearly 5x more global warming emissions than lab-reported data show, according to a recent report.

Growing Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Analysts studied information from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered 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.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior researcher involved in the report. “This gap is widening and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode compared to overall mileage. They determined that just 27% of travel was done in EV mode, while lab assumptions assumed over four-fifths.

Even, when operating in EV mode, pollution amounts were well above lab projections. This occurred because electric motors were not strong enough to operate alone, resulting to engines burning fossil fuels for almost a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed four major automaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra annually in running expenses than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Pressure

Hybrid cars have recently been drawn back into policy discussions as automakers have pressed the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

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

“These findings demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering this data.”