A new light-bulb developed by General Electric Co. to save energy and project a warm glow, will be switched on for the first time at the new J. C. Penney Co. store at Fair Oaks Mall in Fairfax.

The bulb is supposed to use 35 percent less energy than other lighting systems and cost less after several years of use. For example, in a shop about half the size of Penney's 155,000-square-foot store, the new bulbs would reduce the annual operating cost from about $55,979 to $21,833 and over 20 years save $721,440, said Joseph F. Vercellotti, a General Electric general manager.

"Most of this savings in annual operating cost results from the savings in energy requirements of the more efficient Multi-Vapor ii lighting," Vercellotti said.

"We expect the lamp will become generally available by the end of the year which should be in ample time for store and other building planners to factor it into their plans for new construction or rennovation," Vercellotti said.

The lamps should save the J. C. Penny store $22,500 each year in energy costs and about $15,000 in construction for each new store, General Electric officials said. The Penney Co. plans to use the lamps in each new store, Penney's officials said. The Fairfax store is scheduled to open Thursday.