In this gray age of computers, Americans pay a lot of attention to colorful leaders, and a new movement hardly can be called a movement unless it has a messiah. In fact, the alternative energy movement lacked a single charismatic figurehead for so many years that even the super-establishment Atomic Industrial Forum complained.

There is one now. His name is Amory B. Lovins.

He has been compared to Ralph Nader and mentioned in the same breath as Mahatma Gandhi. At 29, technically a dropout, he nevertheless holds a master's degree from Oxford, conferred especially for him though he had only two years there following his two years at Harvard.

In the 1976 Foreign Affairs article that established his reputation (it is now a book, "Soft Energy Paths: Toward a Durable Peace"), he laid out his basic points:

He distinguishes between "hard" technologies, depending on depletable natural resources like fossil fuels and requiring a huge investment and the power apparatus that goes with it, and "soft" technologies, using solar or wind power, which can be developed on a small scale.

Decentralizinge nergy sources will enable us to fit the power to the need. "Why do we need a nuclear plant producing trillions of degrees of heat energy just so we can switch on a light?" he asks. "It's cutting butter with a chainsaw."

Even as the cost-effiency of hard technologies drops, the feasibility of soft technologies will inevitably rise with new improvements.

Society can double the use it gets from its energy sources, with a little effort.

"In other words," he explained in a phone interview yesterday, "we shouldn't simply assume an energy demand as a given, and build power plants according to projections of theoretical future needs. My approach is to ask ourselves what jobs we want this energy for and what is the most effective way to get it."

Lovins will be of several speakers this afternoon at the Sun Day ceremonies near the Washington Monument. Nader, actor Robert Redford, Sen. Charles Percy and others will speak as part of Washington's celebration of Sun Day, a nationwide consciousness-raising effort along the lines of Earth Day.

Though he was not one of the originators, Lovins joined the board of sponsors and has been helping with a speechmaking swing around the country.

"One reason why we need a Sun Day" he said, "is that a lot of people don't know what's actually been achieved already, things that are practical and economically attractive. Even a lot of the solar experts don't know all the stuff that's happening in thousands of places in the world. It's so scattered, we don't have an active grapevine."

The alternative energy movement has become political, as would any movement that threatened any kind of establishment. But Lovins steers away from all that.

"My argument isn't ideological," he said, "it's numbers. That's what makes them mad: I'm using their own figures against them. It's not the eloquence of my arguments: It's just that their way costs too much.

"Actually, this is a deeply conservative movement. It's the nuclear power people who are proposing radical social change, things that will affect all our lives."

There are those who believe that America lacks the national willpower to achieve the reforms Lovins urges in our use of energy.

His response is that the problem here lies with the leaders, not the followers.

"Most of the action I've seen around the country is being taken at the state and local level," he said. "The federal government is lagging far behind. People are turning to solar technology is developing faster than anyone realizes. Washington will be the last to know."

Lovins, who spends most of the year in London as the British representative of Friends of the Earth, a Berkeley-based nonprofit group, has been a visiting lecturer at University of California there this year. In June he will take off for the White Mountains of New England, where he likes to hire out as a guide.

Unmarried, he mostly travels these days, shuttling among 15 countries to testify before government bodies, lecture, write (six books so far) and plan strategy.

Lovins, one observes, is a post-industrial Type. Like Nader, filmmaker Jerry Bruck, I.M. Esfandiary and some others, he is one of those dedicated people who darts around the world like a waterbug with address book and toothbrush, sleeping on friends' living room floors, eating on his feet, living what someone has called an elegantly spartan life.

He wears a calculator and a compass on his belt. He talks fast. He mentions a fiancee in Europe who sounds like a patient person. He takes pictures of mountains, and he's published two books of photos of headlands in Wales.

Someone once said he looked like Woody Allen. That was a mistake, for where Allen is hesitant, Lovins is sure, briskly sure of where he - and the rest of us - is going.

Perhaps the whole question of energy use comes down to what Americans really want. And nobody knows what that is, even the Americans themselves, until forced to choose. In the meantime, all sorts of spokesmen make claims for the people. For instance John F. O'Leary, deputy secretary of the Department of Energy, who has "great respect for Lovins as a thinker," says most Americans simply will not accept any reduction in their material comforts, no matter what.

Yet Lovins replies that the switch to soft technology is already happening around the county. "It's going to be. It's inevitable, eventually. It's just a question of how how hard we want to make it on ourselves."