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Plug-in hybrid cars emit nearly 5x greater planet-heating pollution than lab-reported data show, as per a recent analysis.

Growing Gap In Lab and Actual CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit organization. That differs significantly with laboratory tests, which assumed a 75% decrease in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead researcher participating in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to overall distance. The team found that only a quarter of driving was done in EV mode, while lab estimates suggested over four-fifths.

Even, when operating in EV mode, pollution levels were well above official projections. This occurred because electric motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for almost a third of the distance completed in EV mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs could pay about €500 extra annually in operating costs than is estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant car industries.

Some senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after a long period in which parts of the automotive sector claimed there was insufficient data to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” the expert stated. “Any policy adjustments concerning PHEVs should be made with extreme care and in the light of this data.”