Real-world fuel consumption of plug-in hybrids is 300% higher than official ratings

The average real-world fuel consumption of plug-in hybrid electric vehicles (PHEVs) in Europe is around 300 per cent higher than official tests and closer to that of internal combustion engine (ICE) vehicles than battery electric vehicles (BEVs).

This is the conclusion of a new report published last week by German research organisations Fraunhofer ISI, the Oeko-Institut, and the IFEU, which analysed on-board fuel consumption meters (OBFCM) from approximately one million PHEVs registered in Europe between 2021 and 2023.

The European Environment Agency (EEA) has since 2021 collected data from OBFCMs covering the entire vehicle life cycle of a PHEV including total mileage, fuel consumption, technical vehicle data such as electric range and official CO2 values, and most importantly the number of kilometres driven in a PHEV’s different modes – battery only mode, battery charge sustaining mode, and ICE only.

According to the new report, OBFCM data shows that the average real-world fuel consumption of PHEVs is 5.9-litres per 100-kilometres (l/100km).

This is about 300 per cent higher than the average of between 1.6 and 1.7 l/100km used in WLTP testing, and only slightly lower than the average for combustion engine vehicles of approximately 7 l/100km.

The reason for this is that the WLTP testing cycle wildly overstates the number of kilometres a PHEV will travel on battery-only mode.

Current “utility factors” for PHEVs – the standardised assumption that reflects the share of total driving powered solely by electricity – assumes that a PHEV with a 60km range will cover over 80 per cent of that distance using only its battery.

Data from actual PHEVs on Europe’s roads show, however, that PHEVs only cover around a quarter of their kilometres on battery-only modes.

New UF thresholds are set to be introduced across the European Union to better reflect historically real-world driving – down to 54 per cent in 2025/26, and 34 per cent in 2027/28 – but, in many regards, the damage is already being done.

European advocacy group for clean transport and energy, Transport & Environment, published their own analysis of OBFCM data in September of last year showing that real-world emissions from PHEVs are five times higher than official tests would suggest.

In fact, OBFCM showed that real-world CO2 emissions from PHEVs were 3.5-times higher than official tests in 2021, and have only increased in the years following, to nearly 5-times higher in 2023.

And numbers published by the European Automobile Manufacturers’ Association in January showed that PHEVs accounted for 9.4 per cent of all new cars registered across the EU in 2025 – demonstrating their continued popularity in region. Even worse, non-plug-in hybrids accounted for a whopping 34.5 per cent, the largest segment for new car registrations.

While adjusting the UF threshold for PHEVs will eventually help to close the gap between real and promised fuel consumption, some carmakers and other stakeholders are calling for these adjustments to be suspended or postponed.

Doing so, however, “would significantly weaken European CO2 regulations for passenger cars and lead to additional emissions in the transport sector of up to 25 million tonnes of CO2 in Germany alone,” wrote the Oeko-Institut’s Peter Kasten.

“In order to reduce the gap between actual consumption and official values to a level similar to that currently seen for combustion engine cars, it would be necessary to further tighten the UF for PHEVs.”

Modifications to the PHEV UF threshold are not the only changes being advocated in the EU, with the Commission announcing in December a proposed revision to the bloc’s CO₂ emissions standards for cars and vans that would replace its original zero-emission target with a lacklustre 90 per cent reduction, despite the ongoing trickle of evidence condemning cars with an internal combustion engine.

Transport & Environment (T&E) highlighted in early February the potential mayhem that such a revision would wreak on the European car market, claiming that the “proposed changes would mean keeping the combustion engine and hybrid alive and rewarding the laggards.”

“It’s like hedging your bets when there’s only one horse in the race,” said Lucien Mathieu, cars director at T&E.

“The world is going electric, but the EU proposal would divert investment into other technologies that won’t deliver for the climate or the economy. The current 2035 target provides the investment certainty Europe needs to scale up EV production and compete globally.”