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Plug-in hybrid electric vehicles release almost five times greater planet-heating pollution than lab-reported data show, according to a recent analysis.

Widening Discrepancy Between Official and Actual Emissions

Statistics shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a advocacy group. That differs significantly with laboratory estimates, which assumed a three-quarters decrease in pollution.

Analysts examined data from in-vehicle energy use meters of 800,000 cars registered in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” stated a lead researcher participating in the report. “This gap is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode relative to overall distance. They determined that just a quarter of travel was done in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were well above official estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines using fossil fuels for nearly a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 more per year in operating expenses than is estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with large automotive manufacturing.

Some high-level officials have suggested PHEVs as a potential “flexibility” option to introduce in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was too little information to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert stated. “Any policy changes concerning PHEVs should be implemented with utmost care and considering this data.”