Editor's note: An earlier version of this story reported an incorrect amount of spending on capital projects since United Water's last rate increase in 2009.

Declining water usage and costs for infrastructure are contributing to United Water Idaho’s request, which could cost customers about 19 cents a day.

United Water estimates the increase, if approved by the Idaho Public Utilities Commission, would raise about $7.6 million a year and boost annual revenues from $38 million to almost $46 million. Any rate change would take effect in March 2012.

Commercial rates would increase 19.1 percent

The company spent more than $20 million in capital investment since its last increase in 2009. One project, running a larger water line down Hill Road from Harrison Boulevard to 36th Street to boost water pressure north of Hill Road around 36th Street is costing about $2 million and is scheduled to be completed by fall, said Mark Snider, company spokesman.

The proposed increase also is a product of falling consumption. Water usage has dropped by 23 percent from 2003. Part of the drop reflects slowed growth in the residential market.

A cooler than usual spring also meant many customers delayed turning on their sprinkler systems, Snider said.

Conservation and more water-efficient appliances also are playing a role, Snider said.

“Almost three-quarters of our revenues are variable based on water usage, despite the majority of our costs for operating the water system being fixed costs,” said Greg Wyatt, United Water Idaho vice president and general manager.

United Water Idaho serves about 240,000 people in the Boise area.

Bill Roberts: 377-6408