White-collar federal workers and retirees typically will pay about four times more for their health coverage next year than will postal workers, even though both groups use the same plans and get identical coverage and benefits.

Because of their union contracts, the U.S. Postal Service's 800,000 postal employees get a major financial break on health insurance.

The service pays a much bigger chunk of employee health premiums than other federal agencies.

The insurance perk was considered a nice benefit when it was included in the postal union contracts several years ago.

But as health premiums have skyrocketed -- they went up 13 percent this year and will rise an average of 4.8 percent in 1991 -- the favorable premium- splitting arrangement has put much more money in the pockets of postal workers.

It also has become a major cost item to the Postal Service, which says it spends 80 cents of every dollar it takes in for the pay and fringe benefits of workers.

The semi-independent Postal Service is by far the largest federal agency.

It dwarfs its nearest rivals, the Department of Veterans Affairs and the civilian work forces of the Army, Navy and Air Force.

Next year, non-postal federal workers will pay $16.92 every two weeks for single (self only) standard-option coverage with Blue Cross-Blue Shield. A postal employee in the same plan will pay $4.23 every two weeks.

Federal workers who pick the standard-option family plan offered by Blue Cross-Blue Shield will pay a premium of $35.55 per pay period. For the same plan, option and coverage, postal workers will pay $8.89.

The total cost of the Blue Cross-Blue Shield single standard-option plan next year will be $67.68 every two weeks.

For non-postal workers, federal agencies will pay $50.76 of that premium. But the Postal Service will pay $63.45 for its employees, leaving the employee to pay the remaining $4.23 per pay period.

Non-postal workers in the popular GEHA health plan next year will pay $20.14 every two weeks for single coverage and $41.38 for the family plan.

Postal workers who take GEHA -- and get the same coverage -- will pay $5.51 for single coverage and $10.35 per pay period for family coverage.

Postal employees get equally big savings when they enroll in one of the many health maintenance organizations that are part of the federal health program.

Postal workers who take the Kaiser single health plan here will pay $3.89 per pay period. Those in the family plan will pay $10 every two weeks.

Non-postal federal workers in Kaiser will pay $15.56 and $39.98, respectively, for the same option and coverage.

Tomorrow we will list the 1991 premiums that non-postal federal workers will pay if they pick a health maintenance organization.

Postal workers, again, will pay about one-quarter of those amounts.