A: A cooling degree day (CDD) is a measurement used to translate each day’s temperature to the energy demands of air conditioning. Cooling degree days can be used to compare the current summer to past summers. It can also be used to compare the heat in one part of the country with another. For example, cooling degree days can be used to help explain variances to prior years’ electricity consumption. This is especially helpful if you are able to “componentize” your consumption/usage data from your rate and total cost data, which can be done using NWP’s UtilitySmart or a similar service. A sister organization of the National Weather Service keeps records of CDDs per month (and per week) at the national, regional, state, and major city level, which you can find here.
Nerdy bonus information: You can calculate cooling degree days by subtracting 65 from a day’s average temperature. For example, if the day’s high is 100° F and the day’s low is 70° F, the day’s average is 85° F. So, 85 minus 65 = 20 CDD. Another handy link is (national/regional/state) temperature rank.
For example, you may have heard that July 2012 was the “hottest month on record in the USA.” The national temperature rank for July 2012 was 118. But it turns out that July 2011 was pretty darn hot, as well. It came in at 115, which means 2012 was only 2.6% hotter than prior year.
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