Washington Gas Light Co. yesterday reported an 11.4 percent rise in earnings over the 12 months ended Aug. 31, citing higher rates, more customers and colder temperatures in the period for the increase.

The utility, which reports 12-month figures each month and whose current fiscal quarter ends Oct. 31, said its income in the latest 12-month period was $18 million ($3.28 per share), compared with $16.2 million ($3.47) a year ago. Per-share earnings declined because of an increase in the amount of common shares outstanding.

Revenues for the period rose 23 percent to $667.2 million from $511.7 million a year ago.

Two other local companies yesterday reported slightly lower quarterly earnings despite increases in revenues, while a third firm, RPS Products Inc., which has filed for protection under federal bankruptcy laws, reported losses for the quarter and fiscal year.

Bowl America Inc., a Springfield-based bowling center operator, said it earned $270,533 (21 cents) in the quarter ended June 27, off from $289.141 (22 cents) a year before. Sales, however, rose to $3.9 million from $3.8 million in the period. For the year ended June 27, the company earned $1.5 million ($1.11), up from $1.4 million ($1.06) a year ago. Sales rose to $16.8 million from $16 million. The company said year-ago figures for the fourth quarter were aided by a tournament hosted by the company, which operates bowling centers in Washington, Baltimore, Richmond and Florida.

Schwartz Brothers Inc., a Lanham-based record distributor and retailer, said income dipped to $2,569 (zero cents per share) from $7,896 (1 cent) in the quarter ended July 31, on sales of 10.6 million, up from $10.3 million a year ago. For the first half, earnings were $7,258 (1 cent), off from $10,248 (1 cent) in the first six months of 1981. Sales rose to $21.5 million from $20.1 million in the half.

The company said start-up expenses for two new Harmony Hut stores and higher interest costs put a damper on income, while strong sales of video products spurred revenues higher.

RPS Products, a Baltimore-based retailer, said it lost $241,000 in the three months ended June 30, compared to a $2.2 million loss the year before. Sales sank to $3 million from $7 million in the period.

For the year ended June 30, losses totaled $2.2 million, down from $4.1 million, while sales plunged to $13.9 million from $32.2 million.

Company officials attributed the drop in sales to the closings of several stores in an effort to improve the chain's financial picture. RPS filed during the third quarter for protection from its creditors under Chapter 11 of the federal bankruptcy act. It is still working on a reorganization plan under that act.