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Plug-in hybrid electric vehicles release almost 5x greater planet-heating emissions than official figures indicate, according to a new report.

Growing Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel cars, according to analysis carried out by a advocacy group. That contrasts significantly with lab tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a lead researcher involved in the report. “This gap is growing and creates a significant problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall mileage. They found that just 27% of driving was completed in EV mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, emission levels were well above lab projections. This happened because EV motors were insufficiently powerful enough to operate independently, resulting to engines burning gasoline for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 more annually in running expenses than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV cars are obviously way off the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been brought back into political debates as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and opposition from member states with large automotive industries.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after years in which parts of the car industry argued there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “Any policy adjustments concerning PHEVs should be made with extreme care and considering that evidence.”