Rising fuel costs will soon affect O'ahu water bills, as the average household will pay an additional $1.22 per month to cover unexpected energy cost increases incurred by the Honolulu Board of Water Supply.

The "power cost adjustment," to begin July 1, is on top of a scheduled 10 percent rate hike that also takes effect July 1.

A typical O'ahu household using 13,000 gallons of water per month will see its bimonthly bill rise from $63 to $71.50.

The power surcharge is being added because the board's energy costs for the fiscal year that ended June 30, 2007 were $5.65 million higher than expected, the agency said at www.boardofwatersupply.com.

That extra cost was incurred even after the board anticipated, and budgeted for, a 19 percent increase in energy costs in fiscal year 2006-07.

The board is authorized to add the power surcharge, though it has been many years since the last time it has done so, agency spokeswoman Su Shin said.

The coming surcharge — 9.4 cents for every 1,000 gallons of water used — will be in effect for the 12-month period ending on June 30, 2009. It may be extended and adjusted if the board needs to cover an energy-cost shortfall for the fiscal year that ends June 30, 2008.

Since early this month the board has included a flier about the power cost adjustment in bills mailed to customers. The board has also gone to Neighborhood Board meetings to discuss the surcharge.

"We haven't gotten a lot of feedback" on the surcharge, Shin said.