Load Growth – August 2017


Ansergy tries to update its load growth at least once a quarter. This used to be an annual task, back when the sole source of WECC actual loads came from the FERC 714, but thanks to the EIA’s Open Data initiative one can now update load growth as frequently as you desire.

We were talking with a potential client in Houston who told us that all WECC utilities were in demand death spirals; all were losing load to distributed generation, energy efficiency, and the ute’s ridiculously high retail rates. That caught me by surprise, I never realized load decay was taking place across all WECC utes, and after running our own research I still don’t realize that “fact”.

Summary Results

Statistics never lie, statisticians often do. There are many ways to compute load growth, the Ansergy method deploys the following :


  • Actual hourly loads from June 2015 through today for 28 WECC balancing authorities
  • Each year’s loads are matched by Week and Day of Week and Hour
  • Actual hourly temperatures realized for each record are added to the dataset
  • Only those records where temperatures are with +- 1 degree are used for computing load growth. We tested 0 deltas and get similar results; using +-1 provides more tests
  • Exclude load deltas greater than 10%; this throws out outliers like outages, freak storms, strikes,  holidays, etc.
  • Three-period matches
    1. 2017 to 2016; 2016 to 2015; 2017 to 2015
  • Average all matches and compute the % change in Current year vs Prior year


The potential client was right, some Utes are experiencing load decay, but most of those are in the Northwest. Chelan PUD matched temperatures on 636 hours and averaged 4.2% lower loads in the “current” year versus the prior. Portland General was nearly as bad, their decay averaged 3.5% across 1754 tests. Pac East and APS have realized the sharpest declines in non-MidC BAs, with 3.1% and 2.3%, respectively.

Five BAs effectively had no changes in loads while the rest have all experienced “load growth”. The three leading in that group are Salt River (+7.7%), IID (+6.8%), and Nevada Power (+3.8%). All three reside in the Desert Southwest and might explain some of those wild June and July Palo  prices we realized this year.

Drop us a note if you’d like to get a copy of the study.