The average daily charge for a hospital bed in the District of Columbia -- $196.50 -- makes Washington one of the major American cities where it costs most to get sick, according to a new survey.

Only four big cities -- San Francisco, Los Angeles, Detroit and Boston -- had higher rates for beds in all three categories: private rooms, semiprivate rooms, and intensive care units. Washington was one of only 21 cities and towns, out of more than 1,700 surveyed, where a single day in an intensive care unit cost more than $500.

When D.C. rates are compared with averages for the other 50 states, they are the highest in the country, according to figures from hospitals surveyed during the last quarter of 1980 by the Equitable Life Assurance Society.

Local health planners and hospital officials expressed surprise at the survey results, but said yesterday several factors may explain the high cost of illness:

Washington's high cost of living.Room rates usually reflect nursing salaries, food costs, utility charges and administrative overhead -- "things that don't get into [charges for medical] testing, operating room time or other billable services," according to Robert B. Johnson, president of the District of Columbia Hospital Association and executive director of D.C. General Hospital. He said the high cost of providing such services here drives up bed rates.

The poor health of some local residents, and the extensive health insurance of others. Johnson said that the high rate of chronic disease among blacks in poor neighborhoods of the city raises hospital costs because so many patients need expensive treatment for complications of cancer, high blood pressure, diabetes and other illnesses. A spokesman for the Health Insurance Institute suggested that the comprehensive insurance coverage of government workers in the area may increase utilization of hospitals and drive costs up.

The large number of hospitals that operate costly training programs for young doctors and serve as referral centers. The District of Columbia's 12 general, nonmilitary hospitals include three run by medical schools and several others -- such as Children's Hospital, Columbia Hospital for Women and the Washington Hospital Center -- that train specialists and offer high technology services to patients referred from the surrounding area. Training programs and elaborate equipment both raise costs.

The absence of a governmental hospital cost-control commission in the District of Columbia.In contrast to Maryland, where a state agency sets limits on hospital charges, in D.C., "nobody regulates the rates -- in fact, at this point we don't even have authority to [do so]," said Robert Oshel, a health planner with the State Health Planning and Development Agency.

Carl Wilson, the agency's director, said his agency will have authority to collect such information once a law passed by Congress in 1979 is implemented. The City Council currently has no plans to establish a rate-setting commission, according to Polly Shakleton, chairman of the human services committee.

Johnson said individual hospitals are currently responsible for voluntary cost-containment efforts, assisted by a committee formed in 1978 with representatives from each hospital, the D.C. Medical Society, the hospital association and other groups. He argued that the impetus should continue to come from the hospitals themselves.

Judging from the trend in local hospital charges over the last two years, the voluntary effort is not working. Between January 1979 and January 1980 the average price of a hospital bed in the city rose 26 percent -- more than the rate in any state -- according to figures published by the Health Insurance Institute. The figures show that the average cost of a hospital stay in D.C. during 1979 was also higher than in any state.

Whether rising costs are braked by local hospitals or by an outside agency, Johnson said the challenge would be striking a balance between public demand for high-quality hospitals and the need to save money. "What we must do is try to define what are reasonable costs for services, and how . . . to know if a high cost is inappropriate," he said.