Plug-in hybrids emit 4.6 times rated CO2, study says

Plug-in hybrids emit far more carbon dioxide in real-world driving than official approval values suggest, according to a study published Thursday by the International Council on Clean Transportation.

The ICCT, a lobbying group, examined onboard monitor data from roughly 920,000 plug-in hybrids registered between 2021 and 2023. It found what it called a “substantial and fast-growing gap” between real-world and type-approval CO2 emissions.

The study said average real-world CO2 emissions were 3.5 times higher than 2021 type-approval values and 4.6 times higher than 2023 values.

Type-approval calculations assume how far plug-in hybrids will be driven on battery power and how far they will be driven using internal combustion engines. The ICCT said the gap grew because regulators assumed larger batteries would lead to more electric driving, but real-world data did not support that assumption.

The ICCT said the divergence misleads consumers about expected energy costs, allows plug-in hybrids to benefit from incentive schemes, and affects assessments of whether automakers comply with emissions rules.

The group urged the EU not to delay a planned 2027 update to the calculations and called for real-world data to guide further changes.

The study comes as some automakers, especially German carmakers, want plug-in hybrids to remain part of the EU strategy to decarbonise the auto sector. Press reports cited in the supplied material say Germany and its allies want rules loosened further to give more place to hybrid vehicles.