Virginia Electric and Power Co., which had bet substantially on nuclear power and coal to meet its generating needs for the balance of this century, said today it now is considering harnessing the wind and burning peat or even municipal waste to meet increased electrical demand expected in the 1990s.

Vepco President William W. Berry said the utility has begun an "unbiased, systematic search for the lowest cost option or combination of options for meeting future demand." If the firm's three-year study shows some nonconventional fuel source can provide power at lower cost than coal or oil, Vepco will use it, he said.

The study, to be directed by Vepco Executive Vice President Jack Ferguson, is expected to cost $2 million in the first year. Berry said he did not know what it would cost in the succeeding two years.

Vepco's commitment to give alternative energy sources a full trial moves it into the very small group of utility companies making such efforts. The leader is Southern California Edison, which has pledged to extract one-third of its power from renewable sources such as sun and wind by 1990.

Vepco's program is less sweeping, involving only a promise to study alternative sources carefully and use them if they are economically and environmentally feasible and if they exist in sufficient quantities within Vepco's service area.

For most of the past decade, demand rose far more slowly than the company anticipated before the 1973 oil embargo, and Vepco has been retreating from the nuclear age by cutting back on new power plants. Vepco canceled construction of three nuclear generating plants and arranged to sell parts of two others.

Nevertheless, Berry said, Vepco expects overall demand to increase substantially throughout the 1990s. By the year 2000, he said, peak demand is expected to increase by 4.7 million kilowatts, to about 13.3 million. Plants under construction will supply 2.1 million, he said, leaving a gap of about 2.6 million kilowatts between maximum output and anticipated demand.

By the end of the century, he said, "we hope the nuclear option will reopen," but in the meantime, Vepco must decide by 1985 how to provide those 2.6 million additional kilowatts.

First priority, he said, will go to reducing that demand by conserving power through solar energy in homes and businesses and "load management," or storing power in off hours for use in peak periods.

To generate any additional power needed, he said, the company will consider these alternative fuel sources and technologies:

* Wood, peat and municipal refuse. A Vepco statement noted that "a large peat bog exists in North Carolina, and Vepco has already carried out a test burn of North Carolina peat at its Portsmouth power station." Municipal refuse -- trash -- often has been proposed as a potential energy source, but Berry said the Vepco study would have to take into account legal or environmental restrictions on its use.

* "Low-head hydro," or the conversion of existing dams to small power plants, possibly in cooperation with local governments. Vepco already is studying reactivation of a hydroelectric plant here.

* Wind turbines to convert wind to power.

* Fuel cells, which convert energy from fuel directly into electricity by extracting hydrogen from it and mixing the hydrogen with oxygen. Vepco will monitor an experimental fuel cell that is scheduled to begin generating next year on the Consolidated Edison system in New York.

* Solar photovoltaic cells, which already exist but are very expensive, and "combined cycle technology," which uses two different technological systems such as a gas turbine and a steam generator to produce electricity. The Vepco study will deal primarily with a system based on gasified Virginia and West Virginia coal.

Berry noted at a press conference that these fuels and systems "all have their proponents. We often hear attractive claims about their advantages, but we lack solid, realistic information applicable to the Vepco service area for comparing total capital and operating costs of the different options on a consistent basis." The new study, he said, will provide that information in time for Vepco to make a decision in 1985 on its program for providing power in 1992.

He said Vepco had excluded from its study other proposed methods of generating power that are not suitable to the climate or terrain of Vepco's service area. Ocean thermal energy conversion, for example, was excluded because temperatures in Virginia coastal waters do not vary sufficiently, and large-scale solar collectors were eliminated because they take up too much land and do not function in cloudy weather.