Snake River dams ramp up as cold weather drives demand for BPA power, BPA, Jan. 13, 2017

A regional cold snap drove loads, or power demand, in the Bonneville Power Administration’s balancing authority area to high levels – topping out on Friday, Jan. 6 at 10,943 megawatts. The balancing authority area is the electrically-defined “geographic” unit within which BPA’s Transmission Services Operations team balances the supply and demand of electricity on an ongoing real-time basis.

As they always have been, the Snake River dams were an important part of the Northwest’s power resource mix during the recent cold snap. While it’s great when it is available, the wind can’t be relied on to blow at the precise time the region needs power and it’s also tremendously variable; during the worst of the cold weather, wind generation ranged from 3,370 MW to 74 MW. And regional loads peaked between 7 a.m. and 8 a.m. – that’s known as “hour-ending eight,” to power system operators – before the sun had risen. But in the cold and the dark, the Snake River dams were hard at work, at times generating nearly 1,300 megawatts to contribute to the region’s energy needs, when the region needed energy the most.

Loads in recent days have moved above 10,000 MW, a level only seen on the system in five other years since 1997. Although loads exceeding 10,000 MW are uncommon, Friday’s peak is not a record; that honor goes to the year 1990, when BPA’s system reached an all-time-high load of 11,970 MW.

However, the peak reached in 1990 included much more load from direct-service industries such as aluminum smelters. These loads have declined significantly as those industries largely moved out of the Pacific Northwest in the late 1990s.

Cold weather drove this year’s peak, driving up electrical demand across the region for heating. According to BPA’s Weather and Streamflow Forecasting team, Portland temperatures reached a high of 34 degrees Friday, 12 degrees below normal. Friday’s low temperature was 17 degrees, which is 18 degrees below normal.

There are different ways that BPA could report its peak loads, however, for nearly all regulatory reporting purposes, it is integrated hourly data that BPA reports. Reporting is not based on instantaneous readings, such as 1-minute averages or 5-minute averages, which are used for other purposes. Integrated hourly data is essentially an average reading of load in the BPA balancing authority area over the course of a full hour, based on many thousands of individual instantaneous readings throughout the hour. It is this hourly data that is reported here.

Friday’s peak was the highest BPA has seen since 2009, when winter demand reached a peak of 10,898 MW. But if load growth continues over time, BPA’s system will likely see a new record in the future, and the Snake River dams will help meet the demand for power.