Average vs. Peak Demand

Below is a chart showing generator output on a single day in Stehekin (August 8, 2019). The average demand in Stehekin is typically below the hydro’s capacity of 180 kW (on this day, averaging 152 kW). In seven instances though, peak demand surpasses 180 kW, requiring the use of the back-up diesel generator (D2). As demand in Stehekin continues to grow, these peaks could increase and occur with more frequency.

Graph showing generator output at Stehekin Power Plant on August 8, 2019.

On a typical day in Stehekin, electric demand peaks during certain times of the day, likely due to energy intensive activities occurring during those times. Similarly, demand will peak at different times of the year, based on recreation and commercial activities, temperatures, occupancy and other factors.

Historic and Projected Energy Use in Stehekin

Historically, electrical load growth has been relatively flat in the Stehekin Valley. Recently, new applications for approximately 2,000 amps of new electrical service are expected to greatly increase the need for electrical capacity in Stehekin.

A graph of past and projected future load growth in Stehekin.

The existing hydroelectric plant and auxiliary D-2 diesel generator are not capable of meeting Stehekin’s power needs if annual loads are greater than 160 average kW.  It is not known exactly when this limit will be reached, but we project sometime between 2021 and 2027.