Hawaiian Electric Co. has asked the state Public Utilities Commission to approve a 3.1 percent rate increase.

HECO said Friday that if approved, any increase wouldn’t go into effect until the middle of 2011, at the earliest. The rate hike would generate an additional $54 million.

The company says the added money would go largely for the cost of major completed capital projects serving electric customers, as well as the increasing cost of operating and maintaining the electrical system on Oahu.

Any increase would vary by customer category and amount of electricity used.

But HECO calculates a 3.1 percent hike would increase the typical monthly residential electric bill by a little more than $4 to around $162.