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Degree Days: How You Can Use Them To Figure Your Energy Use

Degree days are weather data records that measure the outside air temperature for a particular period of time, such as a day, a week, a month or several months. There are two types of degree days: heating degree days (HDD) and cooling degree days (CDD). These measurements can help you better determine how much energy will be required to heat or cool your home. 

Calculating degree days is simple:

  • First, determine a baseline temperature for household comfort (68 degrees is often used for heating, 75 for cooling).
  • Next, add the day’s high and low temperatures and divide by two to determine the average temperature for the day.
  • To determine the degree days, simply find the difference between the day’s average and your comfort baseline.

For example, if the day’s high was 50 and the low was 20, the average temperature was 35 degrees. Subtract 35 from 68 and you get 33 HDD. However, if the high was 100 and the low was 70, the average temperature is 85 degrees. Subtracting the baseline from the average, you would have 13 CDD.

In addition to helping you determine energy consumption and estimate the costs of keeping your home at a comfortable temperature, degree days can also be helpful when you plan to relocate. To determine in advance how expensive heating and cooling might be in a particular area, find historical data or track the weather patterns of that location for an extended period of time. This will help you calculate a fair estimate of the necessary CDD and HDD to maintain a comfortable home in that area.

Degree days can also help you estimate the energy savings that will result from efficiency-enhancing upgrades to your home, such as duct sealing, adding insulation or upgrading your HVAC components. If you’re looking for ways to improve the energy efficiency of your household or would simply like to know more about degree days, speak to one of our trained technicians. Contact Air-Tro today.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).  For more information about degree days and other HVAC topics, visit our website.

Air-Tro Inc. services the greater Los Angeles area as well as the metro areas of Riverside and San Bernardino County.