If trucks “burn” electricity instead of diesel or gasoline, the air stays clean and fuel bills are lower.

In California, electric vehicles’ zero tailpipe emissions are golden because a fight against smog has been under way for many years. That’s why Transportation Power Inc. has been designing and testing heavy drayage and yard tractors. Five of each are now at work, according to President Mike Simon, who hopes to have 1,000 or more electric trucks of various types running by the end of the decade.

TransPower battery-electric tractors are converted from International ProStar daycab models with diesel powertrains at the firm’s plant in Poway, north of San Diego. Engines and manual transmissions are pulled out and replaced with electric components: five large boxes containing lithium ion phosphate batteries; specially engineered electronic inverters and controls; and a pair of electric motors running through an Eaton Ultrashift 10-speed automated mechanical transmission, which multiplies the motors’ power and torque.

Engineers fashioned mounts for mechanical and electronic components, and integrated those with the ProStar’s instruments, which look stock. Much testing has proved out the concept, leading to the building of initial units.

California’s Clean Air authorities and others awarded the company about $25 million in grants and investment since the company’s inception in 2011. About $12 million is being spent on truck development.

One of the operational tractors is being put through the paces in everyday service with SA Recycling, a large scrap metal dealer with facilities on Terminal Island, adjacent to the Port of Long Beach. With a tare of roughly 22,000 pounds, the TransPower vehicle is about 5,500 pounds heavier than a standard diesel-powered daycab tractor. SA gets around this by assigning the electric unit to lighter loads, says David Thornburg, vice president of public affairs.

Victor Cebollos, a senior driver, likes the TransPower tractor, calling it “smooth and quiet.” He also appreciates its clean, fumeless operation. Thornburg explains that it’s part of a long-term emissions-reduction project being run by the Ports of Long Beach and Los Angeles.

The tractor has been very reliable, he says. And with no engine and associated subsystems, it requires little maintenance aside from tires, air brakes and such. Its range of 70-100 miles has been adequate, as it returns regularly for recharging. He expects that SA will lease the TransPower tractor when the trial is over. It’s also economical to run — costing about one-third of diesel.

Simon at Transportation Power says a drayage tractor uses 1.25 to a bit over 3 kilowatts per mile, depending on grades, loads and speeds. Energy cost depends on electricity rates; if it’s 12 cents per kilowatt-hour while charging overnight, the per-mile cost would be 30 cents. That’s less than a third of the $1 per mile with a diesel tractor, based on $4 per gallon and 4 mpg that’s typical in stop-and-go cycles with a lot of idling that drayage tractors see.

“There are situations when charging during the day costs 40 cents per kilowatt-hour, so the cost per mile would be about the same as diesel fuel,” Simon says. “So you have to be careful when you charge.”

Thornburg is aware of what appears to be a high per-truck cost, but understands what much of it represents. “Anything with new technology, you’re paying for the research and development,” he says. “It’s like the switch to 2007 and later-model trucks with DPFs. There was added cost and maintenance expense, and everybody was upset over it. But it was added to the freight rates, and everybody survived and here we are.”

Read Tom Berg's driving impressions of the TransPower truck.