Electricity use in the United States is down an unprecedented 1.9 percent so far this year and appears headed for the first significant annual decline since World War II, government and industry analysts report.

"This has never been the case since the war, during recessions or even at the time of the Arab oil embargo," said Dr. C. William Skinner of the U.S. Energy Information Administration. "The history of electricity in this country has been one of constant growth."

Edison Electric Institute spokesman Kirk Willison said, "Unless a miracle happens, we are not going to see growth in consumption this year."

As of Aug. 28, the institute said, 1.55 trillion kilowatt hours of electricity had been sold this year to industrial, commercial and residential users in this country, compared with 1.58 trillion sold during the like period last year.

A decrease in American electricity consumption of this dimension -- coming atop growth of only 1.1 percent in 1980 and 1.6 percent last year -- means that demand for power in this country, which had been growing at an annual rate of more than 7 percent until the early 1970s, has been virtually stagnant for the past three years.

The only previous year since World War II in which electricity use declined was 1974, when consumption was slightly lower than the previous year as a result of the general increase in prices that followed the Arab oil embargo.

This year's sharp decline in demand, which analysts attribute to the continuing recession, a cool summer in much of the country and an increasing effort by Americans to hold down soaring electricity bills by conserving energy, has major implications for the nation's utilities.

Because of the long lead times involved in building additional generating capacity, utilities in recent years have been bringing into service new power plants that were launched when the annual growth in U.S. electric consumption seemed likely to remain high.

But since demand grew by an average of only 3.2 percent from 1974 through 1979, the fixed cost of operating power plants has grown far more rapidly than operating revenues. This decline in profitability has created serious financing problems for many of the nation's utilities, and the current drop in demand is adding to their difficulties.

Already this year, utilities have canceled 11 nuclear power plants under construction around the country, bringing to 31 the number of planned or partially completed atomic generating units that have been abandoned by American utilities since 1980.

Many of the units now being abandoned were being built to replace uneconomical generating plants fired by oil and natural gas, and utilities will thus be forced to keep some of these less-efficient older plants in service into the 1990s.

"Utilities are through the fat and muscle and are now hitting bone," said Andrew Reynolds, who tracks nuclear power for the Energy Information Administration. "We're talking about plants now where billions of dollars have been invested. And it's not over yet. We have identified a dozen more plants where a significant amount of construction has been completed that are still very much at risk."

The decision to cut back on new construction and keep older plants in service longer means higher electricity costs in the long term. Skinner also noted that oil-burning power plants last year "consumed almost a million barrels a day, so their continued operation adds to our continued dependence on imported oil."

Government and industry analysts agreed that while cool summer weather and increasing consumer interest in conservation were factors in this year's decline in electricity consumption, the most significant factor has been the sharp decline in industrial activity as a result of the recession.

This is illustrated, analysts said, by the differences in electricity consumption in various regions of the country. While electricity consumption in the Mid-Atlantic region, which would include the Washington metropolitan area, was off 1.7 percent for the week ending Aug. 28, consumption in the central industrial states, which have been hard hit by the recession, was off 11.7 percent, Willison said.

The only part of the country where electricity consumption this year is significantly up is the Rocky Mountain region, he added.

Despite the decline taking place, government and industry analysts continue to forecast a nationwide increase in electricity consumption of between 2 and 3 percent per year over the next decade.

"We're in the process of doing a new set of projections that probably will indicate an increase of about 3 percent for 1983," Skinner said.