Trying to find cheaper electricity for Cecil County residents, the Maryland Public Service Commission today will begin considering whether the Conowingo Power Co. in Elkton must solicit bids for electricity rather than routinely buy it from its parent company, Philadelphia Electric Co. Cecil County officials are pressing for competitive bidding as a way to reduce electric rates, which they say are 10 percent to 15 percent higher than in other parts of Maryland. Conowingo serves 35,000 customers in Cecil County and parts of Harford County and York County, Pa. Such companies as Baltimore Gas and Electric Co., Delmarva Power & Light Co. and Pennsylvania Power and Light Co. are willing to supply electricity to Conowingo, which has no generating facilities of its own, according to Roger J. Venezia, director of economic development for Cecil County. The PSC, prompted by changes in federal law, has recently been chipping away at the power-generation monopoly traditionally enjoyed by utilities. In March, the PSC ordered BG&E; to solicit bids for a new power plant from independent power producers. The issue of where Conowingo should get its power comes after the PSC in 1992 granted the company a 27.7 percent rate increase, to be phased in over 10 years. The PSC also ordered Conowingo to study the feasibility of buying power from other utilities. That study, completed in January, found that based on costs and reliability, the company should continue to buy power from Philadelphia Electric. But because of objections to the study's conclusions raised by the PSC staff and others, the PSC decided to hold a hearing. The prehearing conference to be held today will determine the schedule of the hearing, which is expected to last about nine months.