Arizona, where the largest nuclear power station in the country is under construction in the desert about 40 miles west of Phoenix, is shaping up as a key battleground in the escalating debate over the future of nuclear energy.

Though critics opposed to the mammoth Palo Verde generating station cite arguments common to nuclear energy opponents in other areas - they call the facility unnecessary, uneconomical and potentially unsafe - there is another aspect to the debate that is drawing attention: Much of the energy produced at the Arizona site would be channeled to customers in other states.

Utility executives applaud this as a responsible regional approach to energy development that had its beginnings 15 years ago when six utilities joined to build a huge coal-fired power plant near Farmington, N.M. But antinuclear activists see the trend as signaling Arizona's development as an energy-producing colony for states such as California.

More than 40 percent of the power generated by Palo Verde Units 1, 2 and 3 would be exported to Southersn California Edison Co. (15.8 percent), El Paso Electric Co. (15.8 percent) and the Public Service Co. of New Mexico (10.2 percent). Eleven utility companies have an interest in Units 4 and 5. An estimated 60 percent of the electricity produced by these units would be exported, with much of it heading for such southern California cities as Los Angeles, San Diego, Burbank, Glendale, Anaheim, Pasadena and Riverside.

Palo Verde thus would meet southern California's ever-expanding energy needs. California Gov. Edmund G. (Jerry) Brown, Jr., has gained prominence as one of the antinuclear movement's most visible supporters .

"Is he antinuclear or just anti-California-nuclear?" asks April Julian, a spokeswoman for the Consumer Alliance for Responsible Energy, one of 13 groups in a coalition formed to stop development of Palo Verde.

Even Arizona Gov. Burce Babbit has addressed the issue, telling reporters recently: "Let Jerry Brown solve his own problems. I don't think Arizona has a responsibility to become a nuclear power park for the Southwest."

Babbit said "good financial management" dictates that utility companies share the costs of building huge power plants. But he warned that if Palo Verde developed "as a front for California utilities," there would be room for "legitimate concern and examination."

"It's not uncommon for power companies to share the expense of building plants," said Scott Phelps, a Babbitt spokesman. "In return we get a lot of benefit. But if the question is should Arizona become a farm for California nuclear power plants...then that's just wholly unacceptable. They'll get all of the benefits and we'll assume all of the risks."

The first three plant units are about 25 percent complete and are to begin operation in 1983. Approval of Units 4 and 5 is being studied by the Nuclear Regulatory Commission. A decision on an application presented by Arizona Public Service Co. (APS) for the final two units should be reached by the end of the summer.

All five units would contain identical pressurized water reactors. Unlike many other nuclear plants, Palo Verde is not located near a body of water, so the plant will be cooled with waste water effluent from Phoenix and five other surrounding communities. The effluent will be piped from a sewage treatment plant to the Palo Verde site, where it will be retreated and used as condensor make-up water.

Meanwhile, antinuclear forces in Arizona plan demonstrations and a petition to stop construction of Palo Verde.A recent rally in Phoenix drew about 1,400 participants. A drive in underway to gather 53,000 valid signatures on petitions calling for financial and safety responsibility by utilities building power plants in Arizona. A similar measure on the 1976 ballot was defeated by 2 to 1. Uilities spent about $1 million to defeat it; antinuclear groups raised $20,000 to advertise their position.

Nuclear opponents contend they would win a new initiative effort because of the publicity generated by the March 28 Three Mile Island accident in Pennsylvania and because of recent publicity surrounding Palo Verde.

Phoenix newspapers reported in May that about 75 percent of the land purchased for the Palo Verde station was bought from the family of the brother-in-law of APS president Keith Turley.

The land was purchased by the Arizona Nuclear Power Project, a consortium of utility companies from Arizona, California, Texas and New Mexico. Some members of the consortium claim they were never told about the potential conflict of interest. Turley denied there is any conflict, and said members were informed.

Contractors responsible for the design and engineering work - the Bechtel Corp. and Combustion Engineering Inc. - were sued for $300 million in 1974 by a Michigan utility company that claimed the two firms were grossly negligent in the construction of a nuclear facility in Palisades, Mich., and that they were responsible for "unreasonably dnagerous conditions" there.

The suit said Michigan utility consumers paid millions of dollars to purchase replacement power for Palisades.

Arizona utility officials counter that the track record of Bechtel and Combustion is solid, and that Combustion's power reactors "had the best operating record of any in the country" in 1977.

All defendants eventually agreed to a financial settlement, with Bechtel paying Consumers Power $14 million in May 1977 and Combustion Engineering paying $40.5 million in December 1977.

Recent economic developments could play a role in the petition drive. In May, APS announced a one-year delay in the plant's initial operation, which will cost $324 million, bringint the projected cost of Units 1, 2 and 3 to $3.24 billion, up 16 percent since 1973.

Caught in a debate over Palo Verde is Babbitt, a liberal Democrat who was recently appointed to the presidential commission charged with investigating Three Mile Island.

The governor has supported Palo Verde, claiming that nuclear power is a necessary part of Arizona's energy future until alternatives can be developed in 10 to 20 years.

Babbitt's chief executive assistant, William Reilly, is a former board chairman of APS. Babbitt's aides say Reilly has voluntarily removed himself from all executive discussions about Palo Verde because of the potential conflict of interest, and that he has sold virtually all of his stock in the utility company.

Babbitt recently suggested that the state prohibit residential development within 10 miles of the plant since "nuclear power plants and residential development are incompatible."

He said creation of a buffer zone is an important way to minimize risks like those at Three Mile Island. CAPTION: Picture, Fence with bilingual warning signs guards the site of the Palo Verde nuclear plant under construction. By John McDonnell - The Washington Post