Some residential customers will have up to 10 additional days to pay their monthly Pepco bills without a late penalty under a plan approved yesterday by the District of Columbia Public Service Commission.

The extended payment plan is available to certain D.C. customers whose main source of household income is from Social Security, Aid to Families with Dependent Children or other government-sponsored, low-income programs. To get the extra payment time, an individual customer must apply to Pepco, which will screen applications for acceptance.

Application information will be sent to potentially eligible customers in the May bills, a Pepco representative said.

Under the plan, there will be a grace period for a qualifying customer whose electric bill normally is due a few days before the person's assistance check arrives. For example, the person's bill now may come due on the 25th day of the month, five days before his assistance check arrives. But if the person qualifies for the new Pepco payment plan, the due date for the bill could be extended up to the fifth day of the new month without late payment charges.

An estimated 20,000 residential customers, mostly senior citizens, may qualify for Pepco's extended payment plan in Maryland, which approved the plan last month, and in the District. The company has no plans to offer the plan in Virginia.