In recent years, there has been a consistent push to electrify vehicles, part of which come from regulators. This has seen not only private consumers increasingly choosing electric cars, but also commercial businesses going electric for medium- and heavy-duty transport. This is because electrification provides opportunities to potentially reduce the total cost of ownership by eliminating the need for fuel and simplifying maintenance. In addition, it brings more stability by protecting fleet owners from rising and volatile fuel prices.
An oft-mentioned challenge in this electrification shift in trucking is the tradeoff between payload capacity and battery weight. Unlike their diesel counterparts, electric trucks need to carry sizeable battery packs, which contribute to the overall vehicle mass and therefore affect payload capacity. In this blog, we look at how the payload capacity of electric trucks with differing ranges compares to that of a diesel truck. To do so, we consider payloads of the two truck platforms in the U.S. and Europe after subtracting the weight of the powertrain. The difference between the two regions stems mostly from the maximum allowable gross vehicle weight — in the U.S., this is 80,000 lb. (roughly 36.2 tonne) while the corresponding figure in Europe is 40 tonne. Note that there are provisions that allow going beyond this weight.
We arrive at the different range values on the horizontal axis by varying the battery capacity between 200 kWh and 1,000 kWh with an efficiency of 1.4 kWh/km (note that we use an average value for the efficiency; some trucks are claimed to have better values). For instance, the Tesla Semi is claimed to have an efficiency of roughly 1.7 kWh/mile (or 1.06 kWh/km). To determine the weight of the battery, we use an energy density value of 160 Wh/kg, which is today’s standard for lithium-iron-phosphate batteries. While the above graph is sensitive to these (and other weight) values, it does accurately represent the relationship between payloads of electric trucks and their diesel equivalents with varying range.
For trucks with ranges under 300 km, electric trucks have payloads almost equal to their diesel counterparts. This drops to about 80% in the EU and 78% in the U.S. at the opposite end (~1,400 km). However, no truck with this high of a range exists today. Most trucks offer ranges between 300 km and 500 km, and the electric trucks in this segment offer payloads of roughly 95% compared to diesel ones (the Tesla Semi is a notable exception with a claimed range of 500 miles or 800 km where the payload ratio is about 90% in both regions).
For short-haul routes, electric trucks are a perfectly capable alternative to diesel trucks in terms of payload. For longer distances, electric trucks do lose some payload capacity, but the difference is not too high. For many applications, the volume will typically begin to play a role before reaching the high end of the weight limit. Furthermore, the weight concessions offered (partly) by both regions compensates for any difference in payload capacity. The EU allows electric trucks to weigh an additional 4 tonne, while states like California in the U.S. allow an increment equal to the weight disparity between a near-zero- or zero-emissions powertrain and a comparable diesel tank and refueling system, with a maximum limit of 2,000 lb. Therefore, payloads in heavy-duty electric trucking will likely not be a restrictive factor in many cases. Other parameters like range or charging times will likely be bigger barriers, depending on the application.