Imagine the scene: along a street in Crystal Bay, Nev., there is a telephone booth, next to which sits an economy-minded sidewalk artist named Paul.

If the street is his studio, the telephone booth is his office. Paul uses the telephone there to place and receive his calls.

Now the telephone rings. Paul answers, and perhaps, not to his surprise, it is Washington calling him again.

This time it is not his friend at the Department of Energy. This time it's somebody else from DOE -- the office of the inspector general -- trying to find out why DOE's telephone bill is running so high.

It turns out that Paul's friend at DOE has called him once and talked for 28 minutes and called him another time, chatting for 38 minutes. Sidewalk artists deserve coffee breaks like anyone else.

Paul's friend at DOE made the calls over commercial telephone lines, and DOE picked up the tab. That is, John Q. You-Know-Who picked up the tab.

Toting up the cost of those calls, plus scads of others, the DOE gumshoes found that the department spent $278,000 for unnecessary commercial long-distance calls in fiscal 1978.

In a report to Secretary James F. Schlesinger Jr., J. K. Mansfield, the inspector general, said that most of the 74,000 calls were personal or business calls that should have been made on leased long-distance lines.

"In other words," Mansfield said, "a large portion of this $278,000 was simply wasted money."

A DOE employe's son made a call from home in Falls Church, Va., to Key Largo, Fla., and talked for 129 minutes, then charged it to DOE. Daddy explained that Johnny was an "unpaid consultant" and assumed he could charge the call.

An employe at DOE made a $435 conference call -- personal, yet -- and two days later made a similar call that cost $696.

Another energy-saver called from his Germantown, Md., office to his Dale City, Va., home 48 times in six weeks. He said 99 percent of the calls were to obtain data from files he left with mama, a new way of leting fingers do the walking.

There were more examples, but Mansfield said in his memo to Schlesinger that he's not satisfied. He is checking into the telephone records of 200 DOE offices around the country for other abuses.

Meanwhile, he said, DOE should set up new rules on telephone use. He also recommended that personal callers be billed for repayment, and that the worst offenders be charged annual leave for the time spent on their personal chats.

Mansfield's memo fell into the hands of Rep. John D. Dingell (D-Mich.), who went into a low-level orbit over "outrageous waste" of tax money.