Elon Musk knows how to make promises. Even by his own standards, the promises made last week while introducing two new Tesla vehicles—the heavy-duty Semi Truck and the speedy Roadster—are monuments of envelope pushing. To deliver, according to close observers of battery technology, Tesla would have to far exceed what is currently thought possible.

Large for-hire carriers and major retailers are reserving their places in line to be among the first to test the all-electric Tesla Semi in their operations.