"Carter energy program is the best thing to happen to me since Ralph Nader," said a Washington lawyer whose clients include a number of companies in the automobile industry.

While phrases such as auto efficiency, gas guzzler tax and coal conversion signify to most of the nation thenation the government's attempts to control the energy crisis, Washington lawyers see them as money in the bank. With the increasing federal involvement, energy has emerged as the newest, hottest growth specialty of the legal profession.

Washington lawyers keep clients across the country informed of the maze-like efforts of the federal government in the energy field. They help prepare testimouy, analyze legislation, help with license and contract applications and try to influence agency regulations. In rare circumstances they do what most other lawyers spend the majority of their time at - preparing legal briefs or going to court.

The need for Washington lawyers in the energy field is growing, said L. Manning Muntzing, a former director of regulation for the Atomic Energy Commission who now is a partner in the newly-formed law firm specializing in energy.

As an example, he cited gas and electric companies across the country that until recently felt no need for a Washington lawyer; most of their business was in state capitals.

Now, however, such federal concersns as licensing for niclear reactors, coal conversion and making utility companies salesmen for home insulation has convinced them "that state public utility commissions are not the final arbiters."

The sums of money involved in government decisions on energy are huge - and so are the legal fees, though lawyers are reluctant to talk about them in dollars and cents terms.

One attorney, however, indicated that a $10,000-a-year client only peripherally concerned with energy matters now pays more than $250,000 for legal advice.

New firms are sprouting up to specialize in the new branch of law, and Texas law firms - which long have represented gas, oil and pipeline interests in that state - are beefing up their Washington offices to cover federal activities.

Moreover, Washington's old established law firms now find it necessary to add experts in energy law to the roster of partners, joining the traditional specialties such as taxes, anti-trust and securities.

To meet the growing demand for lawyers with experience in the energy field, lawyers are quitting government to go into private practice. At least a dozen have left the Federal Energy Administration in the past two years.

Among those who left the FEA for private law practice are Robert E. Montgomery Jr., former chief counsel who now is the energy specialists at Hogan & Hartson, and Duke R. Ligon, a former assistant administrator who joined the Washington office of the Texas law firm of Bracewell & Patterson.

Eric Fygy, the FEA's acting general counsel, said former FEA lawyers do not appear before the FEA in the first year after they have left to avoid conflict of interest problems. He added, however, that they still can adivse clients and other lawyers in their firm about FEA matters.

The FEA isn't the only fertile ground for recruiting energy law experts.

Former AEC Commissioner William Doub and Muntzing joined with two former congressment - Orcal Hansen, who served on the Joint Committee on Atomic Energy, and Graham Purcell, who comes from oil-rich Texas - to form a firm concentrating in all fields of energy - but because of the partners' experience, dealing especially with neclear energy.

From Capitol Hill, four of the most influential House and Senate staff members have started their own firm specializing in energy. They are William J. Van Ness Jr., former chief counsel of the Senate Interior Committee; Charles Curtis, formerly known as "Mr. Energy" with the House Commerce Committee; Howard Feldman, former chief counsel for the Senate Investigations subcommittee who brought th epresidents of the "Big 7" oil companies to testify under oath, and S. Lynn Sutcliffe, former general counsel for the Senate Commerce Committee

This "revolving door" between government and private law firms has come under increasing fire in recent years.

The incoming president of the American Bar Association, William B. Spann Jr. of Atlanta, has called for a bar association review of the legal ethics of a lawyer moving from government into private practice.

President Carter has made it clear he opposes that kind of movement and he is trying to make it harder for all government officials - whether they be lawyers or not to take jobs in the private industries they have been regulating.

Yet, lawyers here point out, it is natural for an attorney to get a job in private practice specializing in the same field of law he practiced for the government.

Traditionally, bright young attorneys have gone into governmnet service for a few years - and then moved into private practice in the same field. A successful Washington lawyer needs some experience either in government or as a congressional aide, according to many lawyers here.

Right now, private law firms are actively recruiting specialists in energy law - a fields o new that there are few presedents to guide lawyers.

"The law is an inexact science, but the energy field is incredibly so," said John Zentay of Ginsburg, Feldman and Bress, who has been specializing in it for 10 years.

No fugures are available on how many lawyers now specialize in energy, but last month the Federal Power Bar Association changedits name to the Fedeal Energy Bar Association.

In March when FEA Administrator John F. O'Leary asked a group of 20 attorneys how many were specializing in energy law five years ago only one raised his hand.

"Everytime Congress begins to legislate in an area it's a bonanza for lawyers," said one 10-year energy specialist. "As Congress makes the laws more complex, it creates more work for attorneys, but I don't think it is necessarily good for the country."

Energy law is only one of legal specialties that have sprung up over the past five years as Congress legislated in new areas.

Major law firms added specialists in environmental law after a series of cases in which the only real experts were the young attorneys representing envirinmental impact statements, which can cost hundreds of thousands of dollars for major programs, ahs necome a legal subspecialty.

Similarly, the passage last year of pension reform laws created the need for a small group of specialists in that field. Occupational and health legislation spawned specialists in that area.

One of the fastest growing areas of legal specialization is health law, where attempts by federal, state and local governments to control rising health care costs has given birth to a new legal specialty in cities across the country.

This is reflected in the growth of the National Health law Association, which was started four years ago in the backroom of an Atlanta law office by a few attorneys working in the new field of health maintenance organizations. Now there are 1,000 members.

Looking ahead, wise Washingotn Lawyers are advising young graduate looking for work to specialize in consumer protection agency, that will become the hottest legal specialty in the city.

Right now, though, energy is still the busiest new legal specialty.