Baltimore Gas & Electric Co. yesterday asked for permission to raise both gas and electric rates by a total of $147 million a year.

If approved by the Maryland Public Service Commission, the rate increase would add $5.48 a month to the electric bill of the average Baltimore G & E customer and would increase the average gas bill by $1.15 a month.

The company said the rate increase was needed because of "the continuing effects of soaring inflation" on the cost of providing utility service.

The Baltimore-based power company, whose service area extends into the Washington suburbs, said the higher rates it is requesting are within President Carter's inflation-fighting guidelines.

Most of the increase -- $123 million a year -- would be in electric rates. The company also asked to charge its customers $22.5 million a year more for natural gas and $1.5 million a year for steam, which is sold to large office buildings and industries.

Baltimore Gas said much of the rate increase will be needed to pay for the cost of new facilities to meet the growing demand for power. The company plans to spend $1.4 billion on new plants in the next five years, 75 percent more than it spent in the last five years.

About $300 million of that total will pay for converting oil-burning power plants to burn coal as required by the federal government. Eventually the switch to cheaper coal will save customers money, the company's announcement claimed.

Also included in the rate increase request is the cost of storing -- perhaps forever -- the used, but still radioactive, nuclear fuel from BG&E's Calvert Cliffs atomic power plant.