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Plug-in hybrid electric vehicles produce nearly five times more global warming emissions than official data indicate, as per a new report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. That contrasts sharply with lab tests, which assumed a three-quarters reduction in pollution.

Researchers examined information from in-vehicle energy use meters of eight hundred thousand cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” stated a senior analyst involved in the study. “This discrepancy is widening and creates a serious issue. As a result, PHEVs pollute almost as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to total mileage. The team found that only a quarter of driving was done in EV mode, while lab assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were well above lab projections. This happened because electric motors were not strong enough to operate alone, leading to engines burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled four large automaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in running costs than would be estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car manufacturing.

Some high-level officials have proposed PHEVs as a possible “compromise” solution to include in the legislation.

One external energy policy specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry claimed there was too little data to properly assess actual emissions.

“The results show, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and in the light of this data.”