Emotions play a big role in purchases of passenger vehicles, but fleet decisions are generally driven by numbers, spreadsheets, and the almighty dollar.

And it's in the equation of overall cost where early adopters of electric and other alternative-fuel semis could make a financial killing.

Haulers first out of the gate with electric trucks could operate them at a significant cost advantage over diesel-powered counterparts—and there will be no pressure in early days to reduce transportation prices.

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According to a post on the crowd-sourced financial platform Seeking Alpha, it could take 15 to 20 years for operators to make the switch away from diesel and toward alternatives like electricity, hydrogen, or compressed natural gas (CNG).

During that time, early adopters will have a notable cost advantage thanks to manufacturer incentives—free hydrogen for Nikola Motor truck owners, and discounted electricity for Tesla Semi operators, to name two.

"Nikola's seven-year leasing model shows that fuel savings alone will be more than the cost of the monthly lease payment," the piece on Seeking Alpha said.

Nikola One

Nikola One

"Tesla buyers will pay $0.14 per mile for electricity from Mile One. That is an added cost of $140,000 for the Tesla truck over a 1,000,000-mile useful life."

Nikola Motor and Tesla won't be the only players in the semi space once those companies start delivering trucks.

Traditional manufacturers—names like Peterbilt, Kenworth, Freightliner, among others—are all working on their own semis that jettison diesel power in favor of other forms of propulsion.

READ MORE: Awake at the wheel: Tesla is far from alone in electric trucks

Even diesel-engine producer Cummins is hedging against diesel with its purchase of Brammo, the electric motorcycle startup, to gain knowledge in the electric propulsion space. (Brammo's Empulse motorcycle was sold to Polaris for continued production under the soon-to-be-defunct Victory brand.)

Once fleets become mostly driven by electricity, hydrogen, or compressed natural gas, we may see a reduction in transportation costs should those methods of propulsion turn out to be cheaper without fuel incentives.

Both Tesla and Nikola Motor are expected to deliver their first semis in 2020.

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