Transportation is the largest source of greenhouse gas (GHG) emissions in the United States and heavy-duty trucks, or semi-trucks with a gross vehicle weight >26,000 lbs, are responsible for around 15% of U.S. transportation energy use and GHG emissions – a share that is projected to increase in the future. Electrifying these vehicles would be a significant step toward transportation decarbonization. While major technology advancements and recent policy support are improving the outlook for heavy-duty truck electrification, the opportunity for battery electric vehicles (BEVs) in heavy-duty trucking remains highly debated due to concerns about battery weight, vehicle range, and charging requirements.
In this Nature Energy paper, we focus on short-haul operations (≤200 miles) and show that they are prevalent in the U.S. and early candidates for plug-in electric vehicles (EVs) given their short, predictable routes and return-to- base applications, allowing vehicles to recharge while off-shift at their depots. While most people picture semi-trucks carrying heavy loads over long highways and vehicle range is often cited as the greatest barrier for battery electric trucks, in actuality daily range requirements vary. In fact, data suggest that just ~10% of heavy-duty trucks require a primary operating range of 500 miles or more, whereas ~ nearly 80% of heavy-duty trucks operate primarily within a 200-mile range. These trucks account for around 50% of total heavy-duty vehicle energy use and are typically responsible for distributing goods between warehouses and nearby retail establishments. As a result, the vehicles are often characterized by short, predictable routes and off-shift periods at central locations such as a vehicle depot, making them prime candidates for electrification. Ideally, fleets could perform all charging at their depots, where it is convenient, inexpensive, and fully controllable.
We also explore the impact of charging fleets of electric short-haul trucks on the electrical distribution system. Although previous studies have investigated the impacts of added electrical loads on the grid, including light-duty EVs, implications for heavy-duty EV charging are under-explored. We leverage multiple sources, including public cost data, project reports, existing research, and industry expert elicitation, to summarize the types of upgrades required for depot charging at each stage of the distribution system. In addition to the causes and typical costs for upgrades, we also estimate project lead times, which are often overlooked.
In general, we find that as charging loads increase, the likelihood for upgrades further upstream in the distribution system (i.e., distribution feeders and/or substations) also increases. These are generally more expensive and time-consuming and require considerable planning to accommodate. We also show that charging requirements for short-haul electric trucks can be met at common light-duty EV charging rates (≤100 kW) and that most real-world substations studied can accommodate high levels of heavy-duty EV charging without upgrades.
Historically, EVs have not been considered viable alternatives to diesel trucks for commercial heavy-duty operations, but major technology advancements and recent policy developments are providing great opportunities to electrify this sector. As costs decline and zero-emission vehicle mandates and other regulations take effect, electric trucks will be increasingly adopted in future years. This study, performed at the National Renewable Energy Laboratory in collaboration with two electric utilities, fills several research gaps on heavy-duty electric truck charging and its impact on electricity distribution systems and paints a more complete picture of commercial vehicle electrification. As technology continues to improve, and the prospects of vehicle electrification translates into deployment, studies like this can help anticipate and prepare for the effects of this transition and inform a path towards a sustainable future for transportation.