(BOISE, ID) – Idaho Power customers will see a 12.5 percent rate increase this month in what experts are calling the fourth largest in the state’s history. That amounts to a little over $11 more for power customers each month. Officials blame a declining water supply, which impacted hydroelectric output. Additionally, the failure of the Hoku polysilicon plant in Pocatello led to a bad investment on the part of Idaho Power, which lost an estimated $23 million. Officials say the increase will be in effect for a full year.