Last week the company demonstrated one of its buses in San Jose (see the video below). Seattle and San Francisco are also considering buying the Proterra's buses.

In its "default configuration," the bus will travel 25 to 40 miles on a ten-minute charge, depending on the terrain, says the company.

But President and CEO Jeff Granato and Director of Business Development Joshua Goldman are careful to point out that since the buses are made to order, the "default configuration" varies according to the client and the planned use. How much battery goes into a bus "depends on how far the user wants vehicle to go," they told the Industry Standard in a phone interview. For instance, an airport-to-car-rental shuttle bus needs a smaller battery than a school bus.

The fast-charging, lithium-titanate battery cells are manufactured by Altairnano, a leader in the new technology, but the design and fast charger were conceived by Proterra, says Goldman.

As every long-term laptop owner knows, batteries eventually wear out and won't take a charge. But the Proterra executives insist that their batteries are exceptionally durable. They "potentially can outlast the life of the vehicle," they claim.