E.C. Ernst Inc., a Washington-based electrical construction firm, reported yesterday that its first-quarter results improved substantially from a year ago, yielding operating income of $226,000 compared with an operating loss last year of $62,000. Ernst is doing business under Chapter 11 of the federal bankruptcy laws.

Revenues from the firm's contracts totaled $12.7 million this quarter compared with $11.1 million in the same quarter last year.

Net income was down significantly from $3.8 million ($1.07 a share) last year to $105,000 (3 cents) this year. The unusually high net last year is due to collection of $4.2 million in claims owed to the company before it entered bankruptcy proceedings, Ernst officials said.

Evaluation Research Corp., a Vienna-based high-technology consulting firm, reported a 43 percent increase in its second-quarter net income over the same period a year ago.

Profits rose from $81,359 (4 cents a share) in the 1981 quarter to $116,426 (5 cents) this year. The increase came on a jump in second-quarter revenues from $3.1 million last year to $3.8 million.

For the first half of 1982, revenues were $7.1 million compared with $5.7 million last year. Earnings, however, declined from $168,171 (9 cents) last year to $166,769 (7 cents) this year.