The Office of Personnel Management made it official today: Premiums in the U.S. health insurance program, which covers more than 1 million people in the Washington area, will rise an average of 19 percent next January. But for many persons, the rates may actually decline, the agency contends.

Despite the "average" increase, OPM says many federal workers will pay smaller health premiums next year because it anticipates that thousands will shift to less costly plans--which often have lower benefits or require larger out-of-pocket payments for employes--during the three-week open enrollment period starting Nov. 14.

OPM Director Donald J. Devine said that last year more than a million people in the health program "voted with their feet" by switching to less costly plans because of an average 24 percent jump in premiums. Despite that average, OPM said, many employes wound up paying only about 4 percent more because they moved into less costly plans. Because of this, OPM said, the 56 percent premium increase in 1981 and 1982 translates to an actual two-year increase of only 26 percent.

"Our employes and retirees know bargains when they see them," Devine said. "They realize that cost-sharing is the only rational way to deal with spiraling health care costs.".

Over the past several years the personnel agency has attempted to hold down government costs of the health program (it says it pays 61 percent of the premium tab) by "encouraging" carriers not to increase benefits and raise deductibles to force subscribers to pay more out of pocket for treatment. Several of the insurance carriers have taken OPM to court, alleging it is trying to gut benefits.

Here are the 1984 premium changes for most plans covering Washington area employes:

Blue Cross-Blue Shield. This plan covers about half the people in the federal health program. Its high-option one-person plan will go up $4.69 biweekly to $30.05. The family high-option plan will increase by $10.56 to $65.06. The low-option one-person and family plans will go up $1.64 and $2.31 respectively, making the premiums $7.19 and $17.15 biweekly.

Aetna insurance will raise its high-option one-person plan by $13.27, for a biweekly premium of $32.05. The family plan goes up to $40.31, an increase of $23.43. Premiums for the self and family low-option plans will go up $1.30 and $1.01 respectively, raising biweekly premiums to $7.35 and $15.64.

American Federation of Governmment Employees: Self-only plan goes up $2.22 to $16.82 biweekly, and family plan goes up $5.01 biweekly to $34.59.

Alliance Health Plan: One-person plan goes down $2.22 to $8.66, and family plan drops by $9.77 to $33.28.

American Postal Workers: Self-only plan goes up $6.39 to $22.56, and family plan goes up $4.85 to $46.41.

GEBA Health Benefit Plan: Self-only plan goes up $2.71 to $22.09, and family plan goes down 94 cents biweekly to $57.50.

GEHA Plan: Self-only up $3.79 to $10.27; family plan up $5.31 to $18.96.

Mail Handlers: High-option self-only up 56 cents to $6.98, family up 97 cents to $19.82; low-option self-only up 45 cents to $6.26 and family plan up $2.29 to $14.82.

NAGE Plan: Self-only option down $1.19 to $21.18 and family plan up $4.79 to $53.45.

Letter Carriers Plan: Self-only option up $2.61 to $24.48; family up $5.28 to $45.78.

NAPUS Plan: Self-only down 1.22 to $7.49 and family option unchanged at $15.81.

NFFE Plan: Self-only down $2.31 to $15.94 and family down $4.75 to $38.56.

NTEU Plan: Self-only plan up 24 cents to $20.10 and family plan up 99 cents to $45.97.

Postal Supervisors Plan: Self-only up $2.25 to $18.90 and family up $3.96 to $28.03.

Postmasters Plan: Self-only high option up 23 cents to $29.69; family up 73 cents to $62.74; low-option one-person plan up 78 cents to $3.90 and family low option up $1.89 to $9.45.

Group Health: Premiums will drop for all four options. The high-option, one-person plan will be $15.54, the family plan, $46.29; and the low options will drop to $8.52 and $28.12.