Average residential electricity charges in the District will increase by 1 percent later this month, according to a rate change ruling issued yesterday by the District of Columbia Public Service Commission. But commercial users will have their rates reduced by less than 1 percent after the ruling takes effect.

The PSC order, which takes effect no later than Nov. 23, determined how Potomac Electric Power Co. may adjust user rates to provide a $29.9 million, or 5.9 percent, increase in annual revenue approved by the commission July 2.

When it approved the increase last summer, the three-member commission allowed Pepco to raise the rates of all users, except for the very low income, by 5.9 percent, pending the final rate structure ruling.

The PSC's final order allows Pepco to adjust rates only slightly from that 5.9 percent interim rate, so "no sudden jolt" will be felt in upcoming bills, said Howard Davenport, general counsel for the PSC.

Residential bills will increase to an average level of 6.9 percent above the pre-July level, or 1 percentage point more than current levels. Davenport provided figures to illustrate the rate change:

*The typical District customer, who uses 500 kilowatts per month and does not use electricity for water or space heating, will pay $32.90 after the rate change takes effect, up from $31.48 before July and from $32.65 currently.

*The average monthly bill for a customer who also uses electricty for water heating will increase to $59.10 with the new rates, from $54.53 before July and from $59.04 currently.

*A customer with an all-electric home will face an average monthly bill of $68.27 after the change, up from $62.55 before July and $68.09 currently.

Most commercial customers will pay 5.5 percent more than before July but slightly less than they do now. The largest commercial customers will pay 5.8 percent more than they did in June, or about what they pay currently.

The Washington Metropolitan Area Transit Authority will pay 4.1 percent more than it did in June, a drop from its current rate.

The PSC left the rates of low-income customers, previously frozen at pre-1982 levels, unchanged. The PSC urged Pepco to enroll more customers in its low-income heating assistance program, noting that there are many customers who could qualify who are not now participating.

Residential customers will contribute a larger share of Pepco's rate of return under the new rates -- about 2.8 percent, compared with the 2.3 percent share they bore previously, Davenport said. Commercial customers contribute about 10 percent, he said.

In 1983, residential customers in the District and Maryland contributed about 26 percent of Pepco's revenue, commercial consumers contributed 48 percent, the federal government contributed 17 percent and the District government contributed 4 percent.

Last January, Pepco requested a $85.9 million, or 16.7 percent, increase in its annual revenue. The final $29.9 million, or 5.9 percent, increase approved was the outcome of negotiations between Pepco and a number of parties, including the District government, the federal General Services Administration, the D.C. People's Counsel, WMATA, the PSC staff and the Apartment and Office Building Association.

Electric rates for street lights will increase 5.8 percent compared to pre-July levels.

In an effort to deregulate street-lighting service, Pepco agreed in June to sell its street-lighting plant to the District for $14.8 million and to provide maintenance service on a contract basis.

The PSC also decided to leave unchanged the 10 percent rate discount allowed the Blue Plains Wastewater Treatment Plant, Davenport said. The District and Pepco had asked for an increase in that discount to 19.2 percent of the normal high usage commercial rate.