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Plug-in hybrid cars emit nearly five times greater global warming emissions than official data indicate, according to a new report.

Widening Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts studied information from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are decreasing,” stated a lead analyst participating in the study. “This gap is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery power compared to overall mileage. They determined that only 27% of driving was done in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than lab projections. This happened because EV motors were not strong enough to operate independently, resulting to combustion motors using fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 more per year in running costs than would be estimated under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large automotive manufacturing.

Several high-level politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was too little data to properly evaluate real-world emissions.

“The results show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “Any policy changes concerning PHEVs should be implemented with extreme caution and considering that evidence.”