Virginia Electric and Power Company yesterday reported an increase in preliminary earnings for 1980 that President William W. Berry said would reduce the size of rate increases required in 1981.

Vepco said that net income during 1980 was $241.619 million ($1.93 a share) compared with $196.466 million ($1.63) in 1979.

Berry attributed the improvement in earnings to increased sales, improved performance by Vepco's nuclear-generating units and reduced use of oil-fired generators. While Berry predicted that the increase in earnings would modify the need for a rate increase, he also noted that the utility company's yield was still below the level authorized for Vepco by rate-making authorities.

Revenues for 1980 were $2.1 billion, compared with revenues of $1.7 billion in 1979. The balance available for common stock was $184.3 million after payment of preferred and preference dividends. The average number of common shares outstanding was 95.5 million as of Dec. 31, compared with 86.9 million shares a year earlier.

Maryland National Corporation, the parent company for Maryland National Bank, reported record earnings before securities transactions for 1980. Earnings rose to $32 million ($4.47 a share), compared with $25.9 million ($3.63) in 1979.

Fourth-quarter earnings rose to $7.435 million -- also a record, compared with $5.891 million for the same quarter in 1979. The bank attributed the improved earnings to increased net interest income and continued strong performance by the company's non-bank subsidiaries.