Plug-in hybrids are hailed as the epitome of versatility, offering the convenience of gasoline-powered cars coupled with the environmental advantages of battery electric vehicles. However, fresh data suggests that certain official figures drastically underestimate the emissions they generate.
Recent real-world driving data from the European Commission reveals that plug-in hybrids emit approximately 3.5 times more emissions than indicated by official estimates. This discrepancy is primarily attributed to driver behavior: individuals tend to charge plug-in hybrids and utilize electric mode less frequently than anticipated.
Jan Dornoff, a research lead at the International Council on Clean Transportation, remarks, “The environmental impact of these vehicles is significantly worse than what the official figures portray.”
Unlike traditional hybrid vehicles, which incorporate a small battery to marginally enhance fuel efficiency, plug-in hybrids enable fully electric driving for short distances. These vehicles typically offer an electric driving range of around 30 to 50 miles (50 to 80 kilometers), with an extended range using secondary fuels like gasoline or diesel. However, drivers seem to consume considerably more fuel than initially estimated.
According to the recent European Commission report, drivers of plug-in hybrid vehicles emit approximately 139.4 grams of carbon dioxide per kilometer driven, based on fuel consumption measurements over time. Conversely, manufacturers’ official estimates, derived from laboratory tests, peg emissions at 39.6 grams per kilometer driven.
Part of this disparity can be elucidated by variations between controlled laboratory conditions and real-world driving scenarios. Even conventional combustion-engine vehicles tend to exhibit higher emissions in real-world conditions compared to official estimates, although the difference typically hovers around 20%, as opposed to the 200% or more observed with plug-in hybrids.
The primary variance lies in how drivers utilize plug-in hybrids. Previous studies, some leveraging crowdsourced data, have highlighted this issue.
In a 2022 study conducted by the ICCT, researchers scrutinized the real-world driving habits of plug-in hybrid owners. While official emissions estimations suggested that drivers utilized electric power for 70% to 85% of their driving, actual data indicated electric mode usage ranging from 45% to 49%. For company-provided vehicles, the average electric mode usage plummeted to 11% to 15%.
This discrepancy between expectation and reality poses a challenge for drivers who may have purchased plug-in hybrids with the anticipation of environmental benefits and fuel savings. However, if drivers are charging their vehicles less frequently than assumed, the advantages might not be as significant as promised. According to the latest analysis, trips taken in plug-in hybrids only reduce emissions by 23% compared to conventional vehicles, rather than the nearly three-quarters reduction projected by official estimates.
Dornoff emphasizes the importance of pragmatism, stating that maximizing the financial and environmental benefits requires driving the vehicles in electric mode as much as possible.
Closing the gap between expectations and reality is crucial not only for individual consumers but also for ensuring that emissions reduction policies achieve their intended outcomes.
Last year, the European Union enacted legislation slated to halt the sale of gasoline-powered cars by 2035, aiming to curb emissions from the transportation sector, which accounts for approximately one-fifth of global emissions. In the EU, manufacturers are mandated to maintain a specific average emissions value across all vehicles sold. If plug-in hybrids are underperforming significantly in real-world conditions, it could mean that the transportation sector is making less progress towards climate goals than perceived.
Aaron Isenstadt, a senior researcher at the ICCT in San Francisco, notes that the issue of plug-in hybrids failing to meet expectations also persists in the United States. In one ICCT study, real-world fuel consumption exceeded EPA estimates by approximately 50%. However, the disparity between expectations and reality is somewhat smaller in the US, partly due to differences in how official emissions estimates are calculated and partly because US drivers exhibit distinct driving habits and may have better access to home charging infrastructure.
The Biden administration recently finalized new tailpipe emissions regulations, setting emission standards for manufacturers to adhere to. The regulations aim to decrease emissions from newly sold vehicles, with the goal that by 2032, roughly half of all new cars sold in the US will need to produce zero emissions to comply with the standards.
Both the EU and the US have plans to update estimations regarding plug-in hybrid usage, which should facilitate the development of policies that better align with real-world conditions. The EU will implement adjustments to estimates regarding driver behavior beginning in 2025, while the US plans to do so in 2027.
