A Texas company announced plans this week to build a $200 million gas-fired power plant in southern Prince George's County that would sell electricity to Potomac Electric Power Co. and industrial steam to an adjoining manufacturing facility.

The 230-megawatt plant, to be located on a 20-acre site south of Brandywine, would add about 3.8 percent to the Pepco's maximum power capacity of 5,909 megawatts, giving the utility a more comfortable reserve margin in the high-demand summer months.

County officials praised the proposal by Panda Energy Corp. of Dallas, saying it will bring in revenue and jobs, boost the county's industrial base without the environmental damage of a coal-fired facility and help meet the area's energy needs.

"It spells nothing but benefits for the county as a whole and the region," said Alvin J. Nichols, the top industrial development official in Prince George's County.

Panda officials, who have signed a letter of intent with Pepco, said they hope to sign a contract by April, receive regulatory approval by midsummer and begin operating sometime between 1994 and 1996.

The power plant is the fourth independent venture announced in recent months by Pepco. Under the agreements, the company would buy a total of 645 megawatts of electricity that it does not generate itself. Nationally, the independent power industry, which is less regulated than conventional utilities, is producing a growing share of the nation's power demands.

The Prince George's cogeneration plant will be next to a manufacturer of carbon dioxide for soft-drink carbonation. The company's operations would be fueled with waste steam generated by the power facility, according to Edward W. Gwynn, Panda's general counsel.

Gwynn would not say more about the site or manufacturer, saying negotiations are not complete. He said the site is in a lightly populated area.

If Pepco's four proposed independent power purchases come through, and conservation programs meet their goals, the utility "may defer for several years" construction of one of four 125-megawatt units planned at Dickerson in Montgomery County, said spokesman Nancy Moses.

Pepco serves customers in the District and Montgomery and Prince George's counties.

The other proposed ventures include another privately owned plant in Loudoun County, Georgetown University's steam plant and the Dickerson incinerator.

Buying from an independent company allows Pepco to purchase power at a negotiated price that is the same as it would cost to generate its own electricity, but the independent producer bears the risk of cost overruns or other problems.

Another advantage for Pepco and Panda is that the power plant does not require a certificate of need from Maryland's Public Service Commission, although the commission must approve financial arrangements between the two, because of the impact on rates. The plant will need state environmental permits.

Thanks in large part to a 1978 law encouraging utilities to buy from independents, the National Independent Energy Producers, a trade association, estimates that up to half the nation's new electric capacity in coming years will be generated by independents.

Panda's only other facility, a $128 million gas-fired plant in Roanoke Rapids, N.C., began operating in December.

It supplies Virginia Power Co. and North Carolina Power with 175 megawatts of electricity, and it supplies steam to an adjoining textile plant.