Study Finds Many Plug-In Hybrid Cars Rarely Charged, Fuel Use Close to Petrol Models

A new analysis of real-world driving data has found that many plug-in hybrid electric vehicles, or PHEVs, are being used in ways that significantly reduce their environmental benefits, with some models consuming almost as much fuel as conventional petrol cars.

The study, based on telematics data from tens of thousands of vehicles across Europe, indicates that a large share of plug-in hybrids are not being regularly charged. As a result, they rely heavily on their internal combustion engines rather than their electric motors. This leads to fuel consumption and carbon dioxide emissions that are far higher than those recorded under laboratory test conditions.

Real World Data Challenges Official Figures

Under current regulatory frameworks in the United Kingdom and the European Union, plug-in hybrids are certified using standardized laboratory tests that assume frequent charging and a significant share of electric driving. These assumptions produce low official fuel consumption and CO2 figures, which in turn influence vehicle taxation, company car incentives, and manufacturer fleet averages.

However, the new data suggests that many drivers, particularly in the company car segment, charge their vehicles infrequently. In some cases, plug-in hybrids were found to be operating in electric mode for less than half of the total mileage. For certain models, average real-world fuel consumption was reported to be close to that of a standard petrol vehicle of similar size and performance.

This gap between official and real-world performance has important implications for national decarbonization strategies. Transport remains one of the largest sources of greenhouse gas emissions in the UK and across Europe. Policymakers have relied on plug-in hybrids as a transitional technology to reduce emissions while charging infrastructure for fully electric vehicles expands.

Corporate Fleets Under Scrutiny

A significant proportion of plug-in hybrids are registered as company cars, where favourable tax treatment has encouraged uptake. In the UK, benefit-in-kind tax rates for plug-in hybrids have historically been far lower than for petrol or diesel models, based on their official CO2 ratings.

If vehicles are not regularly charged, the anticipated emissions savings may not materialize. This creates a disconnect between policy intent and real-world outcomes. It also raises concerns about the use of public funds to subsidize vehicles that may deliver limited climate benefits.

Some experts argue that corporate fleet policies should include mandatory charging requirements or reimbursement structures that incentivize electricity use. Others suggest that tax advantages for plug-in hybrids should be tightened or linked to verified real-world performance data.

Infrastructure and Behavioural Barriers

The findings do not necessarily imply that plug-in hybrids are inherently ineffective. When regularly charged and driven predominantly on short urban trips, they can significantly reduce fuel consumption and tailpipe emissions. Many models offer electric-only ranges between 30 and 60 kilometres, which can cover typical daily commutes.

However, barriers remain. Access to home charging is uneven, particularly for drivers living in flats or without off-street parking. Workplace charging availability also varies by region and employer. In addition, some drivers may underestimate the importance of regular charging or find it inconvenient compared to refuelling with petrol.

The study highlights the behavioural dimension of transport decarbonization. Vehicle technology alone does not guarantee emissions reductions. User practices, infrastructure availability, and policy design all play a critical role.

Implications for Net-Zero Strategies

Governments across Europe are tightening vehicle emissions standards and preparing for the phase-out of new petrol and diesel car sales over the next decade. Fully battery electric vehicles are widely seen as the long-term solution for light-duty road transport.

In this context, the role of plug-in hybrids is under increasing scrutiny. If real-world emissions remain significantly above official levels, regulators may need to revise testing procedures, fleet accounting methods, or incentive schemes.

The European Union has already updated its vehicle testing methodology through the Worldwide Harmonized Light Vehicles Test Procedure, which aims to better reflect real-world driving conditions. Additional reforms under discussion include adjusting utility factor assumptions, which estimate the proportion of electric driving in plug-in hybrids.

For automakers, the findings could affect compliance strategies under fleet average CO2 regulations. Manufacturers have relied on plug-in hybrids to reduce their reported emissions and avoid penalties. If regulatory treatment changes, investment priorities may shift more decisively toward fully electric models.

A Transitional Technology at a Crossroads

Plug-in hybrids were originally promoted as a bridge between conventional vehicles and fully electric mobility. They offer flexibility, eliminating range anxiety while enabling zero-emission driving over short distances.

The new evidence suggests that this bridge may not deliver its full climate potential unless supported by strong policy signals and behavioural incentives. Without regular charging, a plug-in hybrid effectively functions as a heavier petrol car, carrying both an engine and a battery system.

As governments refine their net-zero roadmaps, ensuring that reported emissions reductions translate into real-world impact will be essential. Transparent data, improved testing methods, and targeted incentives could help close the gap between theory and practice.

For businesses and fleet operators, the message is clear. Achieving genuine emissions reductions requires not only selecting lower-emission vehicles but also ensuring they are used as intended.

Source: www.businessgreen.com