LEAD: Electricity use, up by 50 percent since the first oil crisis, in 1973, will continue to grow strongly in the next few decades, far outpacing the increase in non-electric energy, experts attending a conference at George Washington University here said today.

Electricity use, up by 50 percent since the first oil crisis, in 1973, will continue to grow strongly in the next few decades, far outpacing the increase in non-electric energy, experts attending a conference at George Washington University here said today.

But the source of the new supplies is not clear, the experts say, given concern about environmental damage from fuel burning, and uncertainty among utilities about the financial risk in building new plants.

''Efficiency can continue to have a profound impact,'' said Dr. Peter Blair, the manager of the energy and materials program at the Office of Technology Assessment, speaking of light bulbs, motors and appliances that use much less electricity than older models. But he said, ''Electric use will continue to increase, no matter what happens.''

Several experts suggested that a rebirth of the nuclear industry was the only way to meet demand, but some utility officials were skeptical.

Electricity now supplies about 16 percent of the energy consumed in the country, and will reach 20 percent by 2015, said William McCollam Jr., the president of the Edison Electric Institute, the utility trade association.

Electricity use has grown since 1973 at roughly the same pace as the economy as a whole, or by 2.5 percent to 3 percent a year on average, but the use of oil, coal, natural gas and other nonelectric forms of energy has fallen by 7 percent in the period.

One reason for the growth in electric power is that electricity is taking over tasks formerly met with coal, natural gas or human muscle - making steel, drying the finish on automobiles or milking cows. Electricity is also being used in growing fields that lack alternative power sources, like computers. And air-conditioning use is growing.

The Edison Institute forecasts that electric growth will continue tracking increases in the gross national product until the end of the century, then taper off. Before the first oil shock, electric use was growing twice as fast as the gross national product.

But industry officials warn that planning is not keeping pace. Mr. McCollam of the institute cited one industry estimate that by 1998, the nation would need new generating capacity equivalent to 72 large nuclear plants, but that only 37 percent of that amount is now under construction, most of it coal-fired.

''If we don't reconcile the demand for electricity with our environment, if we limit our electricity options, we'll be in deep trouble,'' he said.

While historically utility companies have provided nearly all electric power, through large power plants, about half the generators now under construction are being built by non-utility generators, which plan to sell their output to the utilities and perhaps to a large industrial customer. The new projects are smaller and can be built faster.

But some utility experts are concerned because most of the independent generators use natural gas, raising the prospect of a dangerous over-reliance on a single fuel source. A primary lesson of the oil crises of 1973 and 1979 was that fuel diversity reduces risk.

Efficiency as Alternative

At the conference, organized by the Institute for Technology and Strategic Research, which is part of George Washington's School of Engineering and Applied Science, some of the experts discussed efficiency as an alternative to new construction or to burning fuel in existing plants.

Dr. Blair of the Office of Technology Assessment, for example, pointed out that the average electric water heater uses about 4,500 kilowatt-hours a year, while the average for those sold in 1988 was only 4,000. The best heaters now on the market use about 2,000, while research and development might lower consumption to 1,000 kilowatt-hours.

If millions of houses switched to more efficient water heaters and other such appliances, Dr. Blair said, the global and regional environment would benefit, along with American energy security. Greater energy efficiency would improve American competitiveness, he said.