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How well do you understand peak demand in the Southeast USA?

image credit: Southern Alliance for Clean Energy (2020)

Here's a test. Can you answer the following three questions about seasonal peak demand in the Southeast USA?

Southeast USA Electric Utility Systems MapIs the Southeast, as a region,

  1. Winter peaking,
  2. Summer peaking, or
  3. Dual peaking?

Is the Southeast's winter peak demand

  1. Increasing,
  2. Decreasing, or
  3. Flat?

At a winter peaking utility in the Southeast, are the frequency of winter peak hours

  1. Much more than,
  2. About the same, or
  3. Much fewer than

the frequency of summer peak hours?

If you answered #3 to all of the questions above, you are already pretty knowledgeable about the Southeast's peak electric load. But there still may be a few surprises in store for you.

Southeast Seasonal Peak Electric Demand, 1998-2018
The Southeast’s peak electric load has shifted from a period of growth to
decline. Summer peaks have been declining, while winter peaks have been
flat – so they have converged.

This week, the Southern Alliance for Clean Energy released "Seasonal Electric Demand in the Southeastern United States." This in-depth look at two decades of hourly load data from 22 utility systems has many findings that will interest electric utility wonks. Here are a few highlights:

  • The Southeast is now a dual peaking region due to declining summer peaks. Individual utility systems are evenly balanced between winter and summer peaking systems. Eight appear to be winter peaking, six appear to be dual peaking, and eight appear to be summer peaking. Winter peaks are more common recent years than in the earlier years of our 20-year analysis. Even so, winter peaks at all utilities are less frequent than summer peaks.
  • Even though the Southeast is a dual peaking region, the vast majority of peak hours occur during the summer.
  • Winter peak variability is higher than summer peak variability, but there is no evidence of an increase or decrease to seasonal peak variability.
  • Summer peak events tend to be of similar length (on average, under 5 hours) and have a similar load shape, although a few utilities tend to have longer duration peak events of up to 12 hours.
  • For most utilities, winter peaks are of shorter duration than summer peaks. However, the most strongly winter peaking systems also have occasional long duration peak events of 14 hours or more and occasionally more than 20 hours.

It's been an interesting project, and sets up a number of questions for future research that we weren't able to answer with the data sets we examined. I'd be happy to discuss our findings, or how we built this unique dataset, in the comments.

John Wilson's picture

Thank John for the Post!

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Matt Chester's picture
Matt Chester on Apr 3, 2020 4:19 pm GMT

Really interesting-- thanks for sharing, John. This information is definitely of high importance to those utilities serving these regions and shows that one-size-fits-all solutions don't exist across the U.S. utilities. Is the Southeast unique in having this shaped profile? I wonder if there are lessons to be learned from this where an international utility market would prove more valuable than lessons learned from other U.S. region's utilities?

John Wilson's picture
John Wilson on Apr 7, 2020 1:21 pm GMT

There are some dynamics that are unique to the Southeast, but I think that two of the somewhat counterintuitive features are probably found in many locations: different peaking characteristics for neighboring utilities, and winter peaking utilities that still have the vast majority of their peak hours in the summer.

Dr. Amal Khashab's picture
Dr. Amal Khashab on Apr 3, 2020 10:07 pm GMT

Hi, Matt

I think it is a regional concept, may differ from region to another. In a wide country like the USA, Canada, China, India, and similar countries you can find that concept. 

Eric Van Orden's picture
Eric Van Orden on May 1, 2020 3:25 pm GMT

Basic question: What is causing the winter peak in the southeast? I would think that air conditioning load in the summer would be pretty significant over anything in the winter. Does commercial and industrial load outweigh that? Or, a lot of heatpumps or resistive heating in the winter? Or, changes in the weather trends?

John Wilson's picture
John Wilson on May 1, 2020 4:52 pm GMT

Surprisingly, I'm not aware of any major utilities that have provided end use data to demonstrate what technologies are driving peaks in the winter. There is lot of speculation about heat pumps and resistive heating, but hard evidence is scarce. Hopefully some utilities will step up and do the analysis and make it public.

What our data show is that the winter / summer variability ratio hasn't changed much over time, so I don't think weather is the culprit that everyone seems to observe. I see winter peaks being more noticable because summer peaks are moderating along with load.

Eric Van Orden's picture
Eric Van Orden on May 4, 2020 4:36 pm GMT

Thanks, John. I poked around on Google and wasn't able to find much either, which is why I asked. 

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