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Plug-in hybrid electric vehicles produce almost five times greater planet-heating emissions than official data show, as per a recent report.

Growing Gap Between Official and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit group. That contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined information from onboard energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a lead researcher involved in the study. “That gap is widening and creates a serious problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery power relative to total distance. They determined that only a quarter of travel was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV emissions allowed four large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more annually in operating costs than would be assumed under laboratory tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little better than regular gas and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn again into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car industries.

Several high-level politicians have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, described the analysis a “very useful contribution” after years in which parts of the automotive sector argued there was insufficient information to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” they stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering this evidence.”