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How Often Do Owners Actually Charge Their PHEVs?

go ultra low electric vehicle on charge on a london street
Do Owners Actually Charge PHEVs All That Often?Miles Willis - Getty Images
  • European Commission report examines real-world fuel economy and CO2 emissions data from 600,000 vehicles from 2021, discovering a significant gap between the type-approval figures for PHEVs and real-world data.

  • The report also examined the fuel economy and CO2 data for gas and diesel models, finding a smaller gap between the official WLTP type-approval numbers and real-world data collected from cars.

  • The European Commission plans to change the WLTP test procedures for PHEVs starting in 2025 as a result of this report to account for the observed gap.


For a long time plug-in hybrids have been viewed as a logical stepping stone to a battery-electric future, offering a battery that can be charged along with an all-electric mileage that would be suitable for most local driving tasks and commutes. At least in theory.

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And as EV demand softened in 2023—along with the overall EV adoption rate crawling at a snail's pace year over year—automakers are once again looking at plug-in hybrids to offer energy-conscious buyers an EV-like option.

But a recent study by the European Commission confirms what many in the industry have suspected about plug-in hybrids: People don't actually charge them very often to take full advantage of the EV driving mode.

The report used data collected from some 600,000 vehicles in Europe over the course of 2021, including gasoline, diesel, and plug-in hybrids of both fuel types, using fuel consumption monitors installed in the vehicles to measure actual fuel consumption versus the advertised consumption.

The on-board fuel consumption monitoring (OBFCM) devices have been a requirement since January 2021 in all new cars and small vans sold in Europe, with manufacturers collecting the data remotely and during service visits.

As expected, the actual emissions of gas and diesel vehicles saw a gap between the official type-approval average CO2 emissions and the vehicles' actual consumption as measured by OBFCM devices. Gasoline cars that were part of the study saw a gap of 23.7% on average, while diesel vehicles saw a gap of 18.1%.

european commission phev study chart
The report noted a significant gap in real-world average fuel consumption numbers and CO2 emissions in PHEVs, versus their official WLTP type-approval numbers.European Commission

But this gap was not particularly surprising for study managers or manufacturers.

"Such a gap was anticipated as there are different factors affecting real-world emissions which cannot all be fully replicated in a laboratory test, such as the traffic conditions, landscape, road conditions, ambient temperature, use of air-conditioning and on-board electronics, and driver behavior," the commission noted.

The real surprise was the gap shown by plug-in hybrids that were part of the study, with real-world CO2 emissions being 3.5 times higher, on average, than the WLTP (Worldwide harmonized Light vehicles Test Procedure) type-approval values, which are the European equivalent of EPA numbers. Likewise, real-world fuel consumption numbers of PHEV models were significantly higher than the WLTP values.