The incandescent globe lights that have long distinquished Washington's side streets from more brightly lit major thoroughfares are going the way of their flickering gaslight predecessors.

For the past nine months, Potomac Electric Power Co. crews have been quietly installing brighter street lights in the city's residential neighborhoods under a plan city engineers say will trim more than $1 million from the city's $12 million-a-year electricity bill.

The plan is to eliminate incandescent street lights from the city by 1987 and to replace them with amber-colored high-pressure sodium vapor lights like those that now shine on most major arteries, said Seward Cross, assistant traffic engineer for the D.C. Department of Transportation.

The change has raised again the issue of how much light should be shed on the urban landscape here.

"We are absolutely committed to the plan to rid the city of these bad lights," Cross said. The sodium lights are 2 1/2 times brighter--an attribute that has won the support of police and residents concerned about crime, he said.

He said each sodium light costs at least $20 less to power for a year than the incandescent type. He said lighting engineers also have found them almost twice as efficient as mercury vapor lights, which were the first replacements for incandescent lights and still preferred by many, partly because they are closer to the same color.

But critics of the new lights fear they will turn night even more into day in the city and detract from the ambiance of residential neighborhoods.

Nearly 40 percent of Cleveland Park and Woodley Park residents who responded to a survey conducted by their Advisory Neighborhood Commission opposed the new lights.

I don't think we need them on quiet tree-lined residential streets," said Betty King, a Cathedral Heights resident for four years. "I think they are going to be very garish, very ugly, and I think the historic districts ought to be protected from them."

About 3,000 incandescent lights on side streets have been replaced, leaving some 28,000 of the city's 60,000 lights to be changed, Cross said.

"My concern when I heard about it was the amount of light around the Naval Observatory," said Kaj Strand, retired scientific director of the observatory and an ANC commissioner. Strand recently organized a meeting between observatory staff and city officials, who assured them the new lights would be installed there in a manner that will not interfere with the facility's giant telescope.

"The high-pressure sodiums are the worst," said Gart Westerhout, the observatory's current scientific director. He said yellow light tends to interfere with the human eye's ability to see starlight.

Making the citywide conversions was an administative decision made by DOT, Cross said. He said the decision preceded and was unrelated to a pending proposal by Mayor Marion Barry to shift the cost of streetlights from the city to residents, a proposal Pepco has said it will fight.

Pepco, which owns 66 percent of the city's street lights and maintains them all, was ordered by DOT to install and pay for the sodium lights. Initially, however, in an effort to minimize opposition, the changeover is being made only in areas where citizens have requested brighter lighting, Cross said.

"They make quite a difference," said Barbara Luchs, an ANC commissioner and resident of Albemarle Street NW, where the lights recently have been installed. "I'm sure a lot of people may not have thought they would like them, but I haven't heard one complaint."

One skeptic is Dr. James Gant, a retired physician and an amateur astronomer for many years, who still sets up his telescope in the back yard of his Klingle Street NW home.

"They say that the light will be directed down. Well, a lot will stray up, " he said. "You know, the night is a very valuable resource and it needs to be protected. We astronomers are very concerned about any increases in light in the city."

"I don't think we can prevent them," astronomer Strand said, however.

Pepco's manager of customer operations, Henry Woodard, agreed, declaring "the incandescent lights are dinosaurs that need to go."