There’s a pleasing symmetry to the synopsis of a documentary film that will be shown at the Maine International Film Festival, July 11-20, in Waterville. “A Road Not Taken” chronicles the fate of a clunky piece of hardware that once sat atop the West Wing of the White House. The film is a road trip of sorts, following the hardware – a solar panel installed by President Jimmy Carter in 1979 – from Washington D.C. to Unity, Maine and then to Atlanta, home of the Carter Library & Museum.

But what may seem like a happy ending becomes troubling, a reaction sought by filmmakers Christina Hemaner and Roman Keller.

In 1979, the second of the decade’s two oil shortages affected U.S. consumers, this one triggered by the revolution in Iran in which the U.S.-backed Shah was toppled by Islamic fundamentalists. While Mr. Carter worked to win freedom for the hostages seized during the overthrow, he saw the larger context in which the crisis played out: U.S. reliance on Middle East oil.

Using the bully pulpit of the office, the president pointed industry and public consciousness toward the future by installing two solar panels on the roof of the West Wing. The panels were not the photo voltaic type which produce electricity, but the lower-tech version which use sunlight to heat water. The water was piped to the staff dining area.

At the time, the Boston Globe reports, President Carter predicted they would “move our nation toward a true energy security and abundant, readily available energy supplies.”

If the still-unresolved hostage crisis did not seal Mr. Carter’s electoral fate in November 1980, double-digit interest and inflation rates did. Ronald Reagan handily defeated the incumbent, the hostages came home, interest rates dropped and the economy eventually was humming along again like a V-8 engine.

In 1986, during Mr. Reagan’s second term, the West Wing roof was replaced, the solar panels were removed and no one seemed to notice when they were not replaced. The panels languished in a government warehouse – picture the final scene from “Raiders of the Lost Ark” – until 1990, when Unity College was able to secure and refurbish the panels. Actress Glenn Close, who has Maine ties, quietly donated $50,000 to the effort.

The panels provided the college cafeteria with hot water until 2005. Last year, the filmmakers took one and secured it to the back of a pickup truck – rigged to run on vegetable oil – and with their camera, headed to Atlanta.

In 1979, the Globe reports, Mr. Carter said: “A generation from now, this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be a small part of one of the greatest and most exciting adventures ever undertaken by the American people – harnessing the power of the sun to enrich our lives as we move away from our crippling dependence on foreign oil.”

Nearly 30 years later, it’s clear which fork the nation took.

“A Road Not Taken” will be shown on July 13 and July 18; see: www.miff.org for more information.