The man credited with hooking the nation on the once-cheap kilowatt, and with infatuating the world with the promise of the peaceful atom, came back to his roots this week to salute the virtues of the wood stove and the shah of Iran.

The man is David Eli Lilienthal, one of the most enduring of the men who served the New Deal. His name is still snyonomous with the Tennessee Valley Authority. He was the first director of the Atomic Energy Commission. At the apex of his career he was an intimate of presidents, a luminary in Washington's power elite, a darling of the liberal establishment, and a champion of democracy. Today speaking at the 46th anniversary of the TVA here, he had to break his schedule for a rest after an impassioned speech in defense of the shah of Iran.

"You can bet someone will take a reward and kill them," predicted Lilienthal, who has spent his last 23 years at the royal family's behest trying to turn the Khuzistan Desert of southwest Iran, the old Persian stomping grounds of Alexander the Great, into a replica of TVA.

He claimed that the new Iranian "barbarism," the "return to the 14th century," had resulted in the execution of some of the best native developers he had been able to recruit for his efforts to duplicate in the Mideast a project that Franklin Delano Roosevelt and Senator George Norris (RNeb.), had created during the Depression to cure the ills of the South.

At the age of 18, the Indiana native began a diary that was published in the 1960s as a five-volume, successful series detailing his controversial career. One of the first entries read, "I am rarely moderate in any of my activities." It is still true at the age of 79, Lilienthal demonstrated in his remarks to press and TVA employees today.

He attacked old friend William Papley, president of CBS, and through him, Walter Cronkite for good measure, for "sensationlist" coverage of the Three Mile Island nuclear accident. The media have covered the event in the same reckless, "yellow journalism" fashion as William Randolph Hearst's papers that "brought on the Spanish Civil War," he charged.

It took only the slightest prompting from a reporter's question for Lilienthal to remember to attack again revered journalist Dorothy Thompson, who once wrote that he was driving Dr. Arthur E. Morgan, the first TVA chairman, to "an early grave" by carrying on a feud about the TVA program.

"He lived to be 93," Lilienthal said of Morgan, the brilliant hydraulic engineer FDR ousted in 1938 in favor of Lilienthal after a controversy over whether Morgan's "basket weaving" prescription for the future of Southern hillbillies or Lilienthal's "evasion, intrigue and sharp strategy" should survive at the agency.

And he accused the nation of so complicating its business and government affairs "that it's very difficult to get things done." He called the Department of Energy a "department of non-energy" and laid the nation's crisis of confidence, its "unraveling," at the feet of leaders who lost the "can-do spirit" that he used to describe FDR.

Asked if the likes of Jimmy Carter and Jerry Brown were examples of "can't do" leaders, Lilienthal only responded, "this nation was able to elect a Catholic, John Kennedy, and survive. It has elected a twice-born Baptist and survived. I suppose if we elected a Zen Buddhist we would also survive."

The occasion for the return of the man who bested Wendell Willkie-onetime chairman of the Southern power holding company, Commonwealth and Southern, and later a Roosevelt political rival, in a battle over whether TVA would string its own power lines into its current seven state region-was the 46th anniversary of the agency that Lilienthal came to in 1933 at the age of 33.

"Most of my heroes turned out to have clay feet," TVA chairman S. David Freeman said today in introduing Lilienthal at TVA's Twin Towers headquarters in downtown Knoxville, which overlooks the city that author John Gunther once described "as the ugliest inside America." "David Lilienthal was different," the man President Carter has directed to resurrect TVA from being "just another utility," said. "He grows in stature as you get closer to him."

Surrounded by TVA employes on their morning coffee break, Lilienthal used that cue to launch an attack on American negativism, to salute nuclear power and to urge in paternalistic fashion that the assembled mix of engineers and secretaries "meet your schedules" for the nation's largest assortment of nuclear power plants, lest the nation lose its best evidence that "you can restore America to itself."

"The excitement of meeting deadlines is what this country needs," Lilienthal said to the generally quiet audience. He reminded them that TVA, under his leadership, had set a world construction record by building Douglas Dam in one year and 19 days in 1942 to supply the power for the Manhattan Project at Oak Ridge, which produced the atom bombs dropped on Japan.

Some TVA engineers greeted the pep rally with befuddlement because the agency, which is years behind now in getting nuclear plants on line, had announced just this week that it was adding up to four years to delay to those already announced schedules. To top that, another engineer asked a reporter, "how could he talk about TVA being the embodiment of democracy when we have been told that we are prohibited from making any statement to anybody on nuclear power?"

The reference was to a directive by chairman Freeman and his namesake on the board, Richard Freeman, that no TVA employes-save themselves-are authorized to comment on the effects of the Three Mile Island nuclear incident on TVA's plans to have the nation's largest number of nuclear reactors on line in the 1980s.

In a tour Thursday of a TVA nuclear plant near Chattanooga, Lilienthal saluted TVA as doing things "right" in comparison to the private utilities who are operating nuclear power plants. That created considerable amazement in the valley because the worst previous utility-related nuclear power incident in U.S. history had occurred in 1975 at TVA's Browns Ferry plant in Alabama when a worker shut the plant down for 18 months by careless use of a candle to check for air leaks in the cable room under the reactor control center.

In the mountains of north Georgia, Lilienthal looked at a TVA demonstration of the value of wood stoves in conserving electricity, and pronounced that another TVA achievement. It was an interesting comment, current TVA critics noted, from a former director who had once hired a public relations firm to promote the use of electrical appliances in the Tennessee Valley.

Lilienthal's vision of volume electric power, delivered to remote rural sites, was responsible for making the TVA region a place where consumers use twice as much electricty as elsewhere in the nation. While TVA rates are still 40 percent lower than the national average, TVA rate payers in the last five years have been in revolt because their electric bills now exceed their social security checks and their mortgage payments.

It was clear to the assemblage of young reporters who confronted Lilienthal in TVA's carpeted headquarters that he had little respect for the inevitable delays that such new technological devices as TV cameras and recording equipment imposed on short news conferences. "Do you remember the days when all a reporter needed was a sharp pencil and some paper," he said sarcastically as the press conference was delayed by the plugging in of various cords to serve the media.

But whatever the visit to the valley meant to him otherwise, Lilienthal made clear he was most pleased because someone asked him about the fall of the shah of Iran. "You must be from the Atlanta papers," he said in an awkward attempt to compliment a reporter for asking about a topic he said "nobody's bothered to ask me about before."

"I assume they will be killed by professional killers," he said of the Iranian royalty. "The queen is fantastically intelligent and handsome," he said, and "the shah has been a conserving friend of the country for 37 years."

Lilienthal, a public figure who got his first job with President Roosevelt because of a recommendation from Justice Louis Brandeis, and who depended on men like Justice Felix Frankfurter for advice during his TVA years, accused modern American intellectuals of "adopting the unchristian attitude that because the shah was brutal, his enemies are justified in brutality."

He deemed the order to assassinate the royal family of Iran, "a major wound in the self-respect of the world." But he denied that he was part of a national lobby to get the family asylum in the United States.

"The most interesting thing is how youthful he is in his thinking," TVA chairman David Freeman said at the end of the week-long visit. "What I've got from this week is that he has given me the courage of his convictions." Freeman said he preferred to associate himself with the former chairman's remarks on TVA and not those on Iran or the charges against the Department of Energy. CAPTION: Picture, David Lilienthal; by UPI