Energy Management

2017 Summer Peak Load Review

4 min read

Summer is a critical time for energy buyers because temperatures have a significant impact on current and future energy budgets. Not only can hot weather increase price volatility in the spot market and drive up forward prices, but it also influences peak demand. Peak demand on the electrical grid is a key determinant of future capacity and transmission costs.

With summer coming to an end, let’s review the weather and peak demand levels so far.

Weather Overview

June-August 2017 is currently on track to be the 10th hottest summer since 1950. This ranking is based on the number of cooling degree days (CDDs), a measure of temperature-driven energy consumption. On a national population-weighted demand basis, this is slightly cooler than the 10-year normal. This is also cooler than the summer of 2016, which was the warmest summer on record. Most of the extreme warmth this summer was limited to the western third of the country. Much of the U.S. east of the Rockies saw a highly variable temperature pattern characterized by a lack of sustained heat. Although periods of hot weather are still possible in late August and early September, the seasonal decline in high temperatures makes it likely that the hottest days of summer are now behind us.

June-August 2017 Temperature Anomalies (Realized + Forecast)

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Source: EarthSat

In general, peak loads this summer have fallen on a year-over-year basis and demand has failed to meet forecasted highs. Milder weather versus last year, afternoon thunderstorm activity, and continued growth of demand curtailment programs has all contributed to a lower peak loads compared to summer 2016.

Note: All loads listed below are not final. These grid operators will be publishing official peak load data at a later date.

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Source: FERC

PJM – The variable temperature pattern this summer from the Midwest to the Mid-Atlantic has generally limited peak loads on the PJM grid. PJM’s summer-to-date peak load of 145.6 GW was set on July 19th from 5-6 pm ET. This peak falls well short of last summer’s peak demand of 151.9 GW set on August 11th, 2016. While early August 2016 was one of the hottest periods from that summer, the first half of August in the PJM region came in cooler than normal for 2017. As a result, PJM’s five highest peak demand levels this summer have all occurred in June and July. The five highest peak demand days so far have been: July 19th (145.6 GW); July 20th (145.3 GW); July 21st (141.8 GW); June 12th (140.9 GW); and June 13th (138.6 GW).

NYISO – Similar to PJM, the New York region has seen highly variable weather patterns this summer. This has resulted in wide swings in peak load. Loads in NYISO peaked above 29 GW on both June 12th and 13th, but failed to rise above that mark again for over a month. A heat wave in late July drove loads above 29 GW on three consecutive days from July 19th-21st, with a year-to-date peak established on July 19th at 29.7 GW from 5-6 pm ET. Due to cooler than normal temperatures in August, loads have failed to rise above 28 GW since the summer peak was established in July. By comparison, loads in NYISO peaked at 32.1 GW in August 2016, while the all-time peak load was set in July 2013 at 33.9 GW.

ISO-NE – Although seasonal forecasts generally favored a hotter than normal summer across New England, loads and temperatures have not lived up to expectations. The highest real-time peak load in ISO-NE this summer stands at 23.7 GW, set on June 13th from 4-5pm when high temperatures in Boston rose to the mid-90’s. This is lower than last year’s peak of 25.1 GW. This has also fallen shy of ISO-NE’s pre-summer forecast which predicted loads would peak between 26.5 GW and 28.9 GW.

MISO – The MISO grid spans a large and diverse geographical area from the Canadian border down through the U.S. Midcontinent to Louisiana. As a result, summer temperature patterns can differ widely across the ISO’s footprint. MISO’s summer-to-date peak load of 120.2 GW was set on July 20th from 4-5 pm CT. This is largely in line with last year’s summer peak load of 120.3 GW which was set on July 21st, 2016. While MISO peak loads this summer were consistent with year-ago levels, loads are still short of 2011’s record high of 127 GW and below MISO’s 2017 peak load forecast of 125 GW.

ERCOT – Ahead of the summer 2017, ERCOT released its annual seasonal resource assessment which predicted peak loads could reach as high as 73 GW based on average historical weather conditions. This would be a new record, eclipsing the grid’s previous all-time high of 71.1 GW set last August. A year ago, ERCOT demand surpassed 70 GW in nine hours during the summer due to hotter than normal weather. Temperatures have been quite hot at times this summer in Texas, with loads setting new monthly records for July on three consecutive days. However, unlike last summer, loads have failed to break through the 70 GW mark so far this year.  ERCOT’s summer-to-date peak load stands at 69.5 GW, set on July 28th from 5-6 pm CT.

CAISO – The western U.S., including California, has endured the hottest sustained temperature anomalies this summer. Triple-digit temperatures were not uncommon across the region this summer. A heat wave in the second half of June caused the California ISO to issue a statewide “Flex Alert” on June 20th and 21st, urging consumers to conserve electricity. Forecasted usage was estimated to reach 47 GW on both days. With the call for conservation, loads peaked at only 44.1 GW during the month of June, ensuring reliability of the grid. So far this summer, the highest load on the CAISO system occurred on July 7th when loads peaked at 45.3 GW. This ended up being lower than last summer’s peak of 46.0 GW despite some exceptionally hot weather in California this year.


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