Plug-in hybrids emit six times their official rating, and carmakers want the fix cancelled

Plug-in hybrids registered in the EU in 2024 emitted an average 145 grams of CO2 per kilometre against an official rating of 24 grams, according to Transport and Environment’s reading of onboard monitor data from 220,000 cars. Carmakers want the 2027 correction to that calculation cancelled, weeks before the Council debates the file.

Plug-in hybrids registered in Europe in 2024 emitted six times their official CO2 rating, according to Transport and Environment. The analysis uses European Environment Agency data from onboard monitors in 220,000 cars.

The real-world average was 145 grams of CO2 per kilometre against an official 24 grams. For 2023 registrations it was 138 against 28, so the gap has widened from five times to six.

Both numbers moved the wrong way. Actual emissions rose about 5% while the official ratings fell about 15%.

Set against ordinary petrol and diesel cars, which averaged 169 grams, plug-in hybrids were 14% cleaner at the tailpipe. A year earlier the advantage was 17%.

These are tailpipe averages rather than lifecycle figures. “Plug-in hybrids are one of the auto industry’s greatest greenwashing stunts,” said Lucien Mathieu, T&E’s cars director.

One assumption produces the gap. The utility factor estimates how much of a plug-in hybrid’s driving is done on electricity, and the more it assumes, the lower the official rating.

Owners who rarely plug in go straight through it. The EU began tightening the assumption in 2025 and a further correction is due in 2027, InsideEVs reported.

ACEA wants that correction cancelled. So does Horse, the Renault and Geely powertrain venture in which Aramco holds 10%, which published a paper in March on how tighter utility factor requirements would harm the industry.

The timing is what lifts this above an accounting row. Brussels has already proposed keeping plug-in hybrids sellable after 2035, by cutting the target from a 100% reduction to 90%.

A leaked industry paper analysed by T&E in April goes further. It asks for 80%, for five-year averaging on the 2030 target, and for the utility factor correction to be dropped.

T&E costed that package at EUR 74B in extra oil imports between 2026 and 2035, and up to 2.4 gigatonnes of additional CO2 to 2050.

The ratings matter because they decide fleet compliance. A car emitting 145 grams counts as 24 towards a manufacturer’s target, and an earlier study put the fines avoided that way in the billions of euros.

Plug-in hybrids were 9.8% of EU registrations in the first half, in a market where hybrids outsell everything. The Council debates the file on 12 October and Parliament votes in November.