The Toyota Mirai hydrogen fuel cell vehicle replaces vroom with quiet, but more importantly replaces stinky, noxious, gas-powered vehicular exhaust with water as its only emission. About one cup of water is produced for each mile a Mirai is driven.

A Honolulu Star-Advertiser test drive Wednesday involved an electric fob, but no key to insert or turn in an ignition, and barely a sound as the electric motor started.

All 151 horsepower offered by the sleek-bodied sedan was never quite fully pressed into service, though on a short stretch of roadway, the Mirai’s acceleration was put to a brief test. Its peppy response was positively received by the car’s four occupants, including Stan Osserman, hydrogen implementation coordinator for the state and fellow test-driver; Rick Ching, executive vice president and chief operating officer of Servco Pacific Inc.; Star-Advertiser photographer Dennis Oda; and a reporter.

It didn’t offer quite the same head-snapping G-forces as did a 2011 ride-along in a Lightning Green Tesla Roadster Sport (288 hp), but the Toyota Mirai is not trying to be a Tesla.

The popular Tesla Model S has from 329 to 691 horsepower, a range per charge of 208 to 270 miles, a base price of $69,900, and weight ranging from 4,647 to 4,830 pounds.

“How much are you paying just to drag those batteries around?” Osserman asked rhetorically.

The Mirai’s 151 hp is derived from hydrogen-powered electricity, which eliminates the need for heavy batteries, so it weighs 4,078 pounds and its range is 312 miles. Its manufacturer’s suggested retail price is $57,500, but there is a $4,000 federal rebate.

The Mirai also is not trying to be a Prius. A Prius Plug-in has 89 horsepower, weighs 4,056 pounds, has a range of 11 miles if only electric power is used, and a base price of $29,990.

“Mirai” means “future” in Japanese, even though 20 years of Toyota’s history have included pioneering work on the vehicle. It is an illustration that the future takes time to build.

Available in Japan since 2014 and in California since October, when it becomes available in Hawaii late this year or in early 2017, its likely buyers will include “early adopters,” those interested in the clean energy movement, and those enamored with technology, said Ching.

Hydrogen fuel cell vehicles exist on Oahu, but they are fleet vehicles belonging to government entities that have their own fueling stations, which represents a hurdle that must be cleared prior to Mirai sales locally. A commercial fueling station must be established, and Servco is working on just such a facility, Ching said.

It isn’t just a matter of installing the hydrogen equivalent of pumps, though. A whole state Department of Agriculture measurement standards branch regulatory mechanism must be created for dispensing hydrogen in consistent qunatities, just like at the gas pump.

It’s easy to measure liquid, Osserman said, whereas gases can be compressed, and the gases’ volume can change with temperature, making consistent, regulated measurement at the consumer level more complicated.

Once built, the hydrogen fueling station will be powered by photovoltaic panels to keep the facility as energy self-sufficient as possible, said Ching. The target time frame for fueling station completion is the end of this summer.

Fueling a Mirai takes about five minutes versus hours to fully charge an electric vehicle.

In a nutshell, hydrogen is pumped into the Mirai’s fuel-cell storage tanks, which have a capacity of 11 pounds. When running, air enters the Mirai’s fuel stack through the front grilles, and combines with hydrogen to create electricity that powers the car’s electric motor and battery.

Despite the electric power under which the Mirai is propelled, it is not eligible for Electric Vehicle license plates the way the law is presently written. Efforts to amend the law to allow for EV licensing for hydrogen fuel cell vehicles encountered some “push-back” from current electric vehicle owners, Ching and Osserman said. EV owners didn’t want competition from vehicles that would take up parking spaces with charging stations they needed, but which the fuel cell vehicles did not. Efforts to amend the licensing law will continue this legislative session, Osserman said.

On the Net: servcotoyotahonolulu.com