What is a Cooling Degree Day?
A cooling degree day (CDD), also known as cooling degree days, is a formula measuring how hot it has been relative to a base temperature over a 24 hour period. The greater the number cooling degree day measurement, the more the air conditioner is likely to be running. Similar in concept is that of heating degree days. The main difference, of course, being that with heating degree days the furnace is the device expected to be working additional time. The way to find out the cooling degree day number is to use the high temperature and add it to the low temperature for the day in question. that number is then divided by two. For example, if the high one day is 90 degrees Fahrenheit (32 Celsius), and the low is 65 Fahrenheit (18 Celsius), the average temperature would be 77.5 Fahrenheit (25 Celsius). This average Fahrenheit temperature would then be subtracted from 65 Fahrenheit (18 Celsius). Although it is possible to calculate a cooling degree day from any temperature, this one was chose
A cooling degree day is used during warm weather to estimate the required energy for cooling indoor air to a comfortable temperature. One cooling degree day occurs for each degree a day s average air temperature is above 65°F. Large cooling degree day values imply warm weather and, thus, a large energy demand for cooling. This Climate Prediction Center page has more about degree days, as does this National Climatic Data Center page. (Answered by meteorologist Tracy McCormick of the National Weather Service in Taunton, Mass.
A cooling degree day is a unit used to relate the day’s temperature to the energy demands of air conditioning. Cooling degree days are calculated by subtracting 65 from a day’s average temperature. For example, if the day’s high is 90°F and the day’s low is 70°F, the day’s average is 80°F. Eighty minus 65 is 15 cooling degree days. 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.
A value used to estimate interior air cooling requirements (load) calculated as the number of degrees per day (over a specified period) that the daily average temperature is above 65 degrees Fahrenheit (or some other, specified base temperature). The daily average temperature is the mean of the maximum and minimum temperatures recorded for a specific location for a 24 hour period. U.S.
A cooling degree day is used during warm weather to estimate the required energy for cooling indoor air to a comfortable temperature. One cooling degree day occurs for each degree a day’s average air temperature is above 65°F. Large cooling degree day values imply warm weather and, thus, a large energy demand for cooling. This Climate Prediction Center page has more about degree days, as does this National Climatic Data Center page. (Answered by meteorologist Tracy McCormick of the National Weather Service in Taunton, Mass.
