Demand for electricity: what's ahead

''The nation's electric utilities face a planning crisis,'' declares a report just issued by the Electric Power Research Institute (EPRI), a nonprofit research institute in Palo Alto, Calif., supported by 630 electric utilities.

''While there is an adequate electric power supply today,'' warns Eugene Oatman, an EPRI program manager and one of the authors of the report, ''there is little room to accommodate economic growth.''

Although the utilities are having little difficulty meeting present electricity demand, the report states that ''if President Reagan's goals for economic growth were to be realized,'' utilities would have to increase capacity by almost 400,000 megawatts in the next 10 years (a megawatt equals 1 million watts).

Financial, regulatory, and environmental problems make it ''far from certain'' even half that amount can be built, according to the EPRI report.

This situation is due in part to the dimming of the vision of a nuclear-powered future, which captured the nation's imagination 25 years ago with the start-up of the first commercial atom-powered plant in Shippingport, Pa.

The EPRI report on the utilities' planning crisis says that although the industry has an adequate electric power supply today, it is utilizing 92 percent of demonstrated capacity. And ''the demand for electricity in some sections of the country reaches as high as 97 percent of the available generating capacity.''

Although the utilities plan to increase their capacity by 200,000 megawatts in the next 10 years, the report says the prospect of reaching that goal is uncertain. And if President Reagan's economic goals were reached, the EPRI researchers warn, the utilities would have to increase capacity by almost 400, 000 megawatts within the same period.

It would cost $200 billion to add 201,000 megawatts of capacity, says the report, and this figure does not allow for repacement of obsolete oil and gas-fired power plants.

EPRI does not suggest specific solutions to this ''crisis.'' The report does cite ''today's licensing and construction programs'' which require long lead time and add to the cost of new coal and nuclear power plants.

The report's conclusion: ''It is unlikely that this planned growth in capacity will be built in time to avoid a shortage.''