TALLAHASSEE, Florida--Advances in medical technology, computers and mass transportation aside, the national magnet laboratory scheduled to open its doors in 1993 probably will keep Tallahassee utility bills down.

That's because the laboratory will use 20 to 30 megawatts of power--roughly a third of the power used by the entire city--to create high-level magnetic fields. That boost to the city's biggest business, selling electricity, will help hold down costs.

The laboratory, which has been at the Massachusetts Institute of Technology for almost three decades, will also put Tallahassee on the scientific map, according to exuberant Florida educators.

They say they used enthusiasm, vision and commitment to attract the lab to Tallahassee from Cambridge.

They admit it was a close race. But the pride and confidence they've displayed since getting word last month that they won doesn't seem measurably diminished by the fight the prestigious engineering school is still waging to keep the laboratory.

"Sour grapes. Too little too late," Florida Chancellor Charles Reed said last week. "They do good science at MIT but on this I don't think that they have paid as much attention to it as they needed to."

There doesn't seem to be much danger of that in Tallahassee, where a common word to describe the importance of winning the lab is "historic."

"This may be one of the biggest things that has happened to our university system," Reed told the governor and Cabinet.

As for the impact on Tallahassee, Reed spokesman Patrick Riordan compared the establishment of the lab to the founding of the city in the early 19th century. The site was picked to serve as the capital of Florida in 1821 because it marked the halfway mark between the population centers of Pensacola and St. Augustine.

The new National High Magnetic Field Laboratory will be located at Florida State University but run by a consortium that includes the University of Florida in Gainesville and Los Alamos National Laboratory in New Mexico, which is run by California's state universities.

Florida officials received the official contract for the lab, which will get $60 million to $70 million in federal funds over the next five years, on Friday.

Also on Friday MIT got something from the National Science Foundation--a brief letter from Mary Gold, chairman of the board that governs the National Science Foundation, saying the independent government agency that supports scientific research with public funds would not change its mind about the lab.

MIT, in turn, protested that second decision.

"When you lose a grant it's a painful experience, but the only appropriate, professional thing to do is move on to the next grant. That's what MIT should be doing," Riordan said Saturday.

Florida's public universities have been in that position. Two years ago the state came close to winning an industry-sponsored semiconducting research center that ended up going to Texas.