It was a day of confusion and waiting for the Washington Hilton's 3,800 guests.

First came the fire, which occurred yesterday morning in the basement transformer room of the sold-out hotel. Then came the questions: Would the hotel reopen? If not, where would the guests, most of them convention-going teen-agers, sleep?

By 5 p.m., they had at least a partial answer: Not at the Hilton.

"We have no electricity," explained the hotel's resident General Manager Bill Edwards.

Edwards, who was in and out of meetings with guests and fire officials for most of the afternoon, said a team of four hotel employes was calling nearby hotels seeking accommodations for the displaced Hilton guests.

For a time authorities considered using the Washington Convention Center as an overnight bivouac for the about 3,700 teen-agers staying at the Hilton while attending the religious Youth Congress '85.

By late last night, however, after complex logistical maneuvering in which the D.C. Office of Emergency Preparedness participated, the youths were checking in to the first of 19 other Washington hotels at which emergency overnight accommodations had been found.

Hilton guests regarded the fire -- and the accompanying inconvenience -- with a mixture of indignation and resignation. No one was injured and some guests said they were thankful for that, but some expressed irritation at the situation and the way it was handled.

Mary McLaughlin, 27, of Boston, stood outside the Hilton entrance yesterday afternoon, holding an I. Magnin shopping bag and looking highly annoyed.

"They kicked us out at 10:30 this morning and that was it," said McLaughlin, who is vacationing in Washington. "They never told us when we could come back or anything. Most of us didn't have any money. I was lucky. I was dressed at the time."

McLaughlin decided there was only one thing to do. "I took the subway to White Flint shopping center ," she said, "and used my credit card." McLaughlin said she had no idea where she would spend the night.

All 1,154 rooms in the hotel had been filled., Edwards said. By the time the fire started, most of the teen-agers had left the hotel to attend the Youth Congress.

"The kids are fine. They're set for the day, even if they can't come back," Youth Congress coordinator Susan Dillon, of Washington, Pa., said in the afternoon. "We believe in God's protection of this conference."

Exactly where everyone would sleep, however, was a matter of continuing concern. Ashok Josh, manager of the nearby Sheraton Washington, said he had been contacted by Hilton employes and had readied "a couple of hundred" rooms for stranded Hilton guests. The Connecticut Avenue Holiday Inn offered 20 rooms.

The scene in the Hilton lobby was chaotic as people waited for hotel employes to escort them upstairs to retrieve their belongings.

Martha Snow, 29, and fiance Earl Anderson, 33, had driven from Richmond Friday and checked into the Hilton for a "romantic weekend."

The couple happened to be the last two guests to evacuate the hotel yesterday morning. They said they were enjoying their 10th floor room just before check-out time, when a firefighter burst in and told them to leave.

"We were looking for the hot spots," said Anderson, 33, "but this was more than we bargained for."