Washington Gas Light Co. yesterday reported higher profits for the fourth quarter and all of 1980, completing a round of improved annual earnings statements by energy utilities that serve the Washington region.

Not counting a nonrecurring accounting change that boosted WGL earnings in 1979, profits from operations over the full year rose to $18.09 million ($3.51 a share) from $14.37 million ($2.65) in 1979, as revenues increased $79 million to $464 million.

In 1979, an accounting change added $4.4 million ($1.01) to final net income of $18.78 million ($3.66) for the Washington-based company, which distributes natural gas throughout the metropolitan area as well as in the Frederick and Shenandoah Valley markets.

For the fourth quarter, Washington Gas earnings rose substantially from depressed levels a year ago of $6.2 million ($1.25) to $11.1 million ($2.38 a share), and revenues rose to $159 million from $125 million, reflecting colder weather with its increases use of gas for heating as well as higher rates. A company statement said WGL still is not earning at a level to cover the cost of capital, however.

Earlier, Potomac Electric Power Co., Virginia Electric & Power Co. reported higher earnings for last year. Pepco, which earned $104 million ($2.10 a share) on sales of $856 million vs. $84 million ($1.73) on sales of $749 million in 1979, attributed its gains to cost controls, higher kilowatt hours sales (up 5.6 percent because of the hot summer) and higher rates.

Delmarva Power & Light Co., in contrast, said 1980 earnings declined to $49 million ($1.60 a share) from $53 million ($1.91) as revenues rose to $520 million from $425 millions. Fourth-quarter profits of the Delaware-based utility, which serves part of Maryland, fell to $7.9 million (21 cents) from $12.3 million (41 cents) while revenues rose to $133.5 million from $107.5 million.

Pargas Inc. of Waldorf said earnings declined in the final quarter of 1980 and for the full year. The LP-gas distributor and coal mine owner said profits declined to $4.05 million ($1.12 a share) in the fourth quarter from $4.32 million ($1.19) a year ago as sales rose to $71.8 million from $57.4 million.

Earnings fell to $11.04 million ($3.03) in 1980 from $12.03 million ($3.30) the previous year although sales were up to $238 million from $183 million. The 1979 results had included a pretax settlement of $3.06 million for reclamation costs claimed under a coal agreement with utility customers.

B.F. Saul Estate Investment Trust earnings in the first fiscal quarter ended Dec. 31 were about $4.5 million (75 cents a share) compared with a loss in the 1979 period of $491,000, Chairman B. Francis Saul II told stockholders at the annual meeting here yesterday. Cash flow from operations soared to $7 million from $850,000, mostly gains from condominium conversions at the trust's apartment properties.

Saul cautioned that the figures are not indicative of possible results for the full year because condominium sales and profits will fluctuate from quarter to quarter. At the meeting, stockholders defeated by a 10-1 margin a shareholder proposal that the real estate trust be liquidated. Stoy, Malone & Co. also was ratified as independent auditors.

Chesapeake Corp. of Virginia reported a 25 percent increase in profits for the year ended Dec. 28 to $23.5 million ($3.83 a share) from $18.8 million ($3.09) in 1979. Sales increased 11 percent to $258 million.

The paper firm, based in West Point, Va., said the sales increse was due primarily to higher average prices, but some 20 percent of the increase was attributed to acquisition of Chesapeake Plywood Inc. in the third quarter of 1980.

Chesapeake President J. Carter Fox said market demand for the firm's products was stronger than expected in the fourth quarter and the sales strength carried over to the first quarter of 1981. Inflation and work on a $51 million expansion project at the mill at West Point will make 1981 a challenging year, Fox said.