Heating Degree Days (HDD) and Cooling Degree Days (CDD)

The following information is disclosed on a quarterly basis in our SEC filings. The information presented here is for informational purposes only and is not intended to be an indicator of past or future results. Weather is only one of many factors that may impact energy sales and we are providing this publicly available information only as a courtesy.

To estimate the impact of weather conditions on energy sales, Pinnacle West typically uses 65°F as the Heating Degree-Days (HDD) threshold and 80°F as the Cooling Degree-Days (CDD) threshold, but does also consider other weather-related factors when it is deemed appropriate. The following table illustrates the months in which the HDD and CDD are most relevant:


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HDD X
X
X
X






X
X
CDD




X X X X X X


 

Pinnacle West and The US National Oceanic and Atmospheric Administration (NOAA) consider different time periods when calculating normal CDD/HDD. NOAA uses a 30-year period for calculation of normal weather and Pinnacle West uses a 10-year average to determine normal weather.

The National Weather Service has a website that provides temperature data for Phoenix Sky Harbor:
http://weather.gov/climate/index.php?wfo=psr

Internal analysis shows a strong correlation between weather conditions at Phoenix Sky Harbor and energy demand in APS service territory.

Weather Indicators - Residential
Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18
Actual
Cooling Degree-Days (base = 80°F) - - - - 143 370 513 435 356 3
Heating Degree-Days (base = 65°F) 129 155 39 - -
10-Year Averages (2006-2015)
Cooling Degree-Days (base = 80°F) - - - - 113 377 494 459 284 53
Heating Degree-Days (base = 65°F) 258 153 53 10 -

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