EGEE 102
Energy Conservation and Environmental Protection

Heating Degree Days Examples

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Example 1

Calculate the HDD for one day when the average outside temperature is 13º F.

Heating Degree Day =  T base   T a   = 65º F  13º F   = 52º F

Calculate the HDD for one day when the average outside temperature is 2º C.

Convert from Celsius to Fahrenheit: 2º C = 35.6º F Heating Degree Day  =   T base    T a   =  65º F  35.6º F   =  29.4º F

Example 2

Given the following data, calculate the HDD for the week:

Example 2: Average Temperature for a Week
Day Average Temperature
Sunday 49° F
Monday 47° F
Tuesday 51° F
Wednesday 60° F
Thursday 65° F
Friday 67° F
Saturday 58° F

Please watch the following (2:21) presentation about Heating Degree Days:

Click here for a transcript of Heating Degree Days video.

Lesson 7a, Screen 20: Heating Degree Day

For this problem, we need to calculate HDD for one full week. The data that is given is each day, what is the outside temperature -- average outside temperature. For example, Sunday, the average outside temperature is 49 degrees F. Monday 47 degrees Fahrenheit, Tuesday it’s 51 and Wednesday it is 60 degrees F and on Thursday it is 65, Friday, 67 and on Saturday it is 58.

Weekly Temperature
Day Temperature (°F)
Sunday 49
Monday 47
Tuesday 51
Wednesday 60
Thursday 65
Friday 67
Saturday 58

So we need to calculate heating degree days (HDD) for each day. One day, that is Sunday, the outside temperature is 65 minus 49 the outside temperature will give you the degree days. Similarly, 65 minus 47° Fahrenheit, one day times 65 minus 51 in this case. One day times 65 minus 60 and one day 65 minus 65. This would be zero. One day 65 minus 67. Remember when it exceeds 65, the heating degree days would be zero. In this case, also it is zero. One day on Saturday it is 65 minus 58.

HDD for Each Weekday
Day Temperature (°F) Calculate HDD
Sunday 49 1 day (65-49)
Monday 47 1 day (65-47)
Tuesday 51 1 day (65-51)
Wednesday 60 1 day (65-60)
Thursday 65 1 day (65-65)=0
Friday 67 1 day (65-67)=0
Saturday 58 1 day (65-58)

This case it is 7.

HDD Totals
Day Temperature (°F) Calculate HDD
Sunday 49 1 day (65-49)=16
Monday 47 1 day (65-47)=18
Tuesday 51 1 day (65-51)=14
Wednesday 60 1 day (65-60)=5
Thursday 65 1 day (65-65)=0
Friday 67 1 day (65-67)=0
Saturday 58 1 day (65-58)=7

These two are zeros, this is 5 and this is 14 and this happens to be 18 and here it is 16. So the total sum is for one full week is 60 degree days.

Sum of One Full Week
Day Temperature (°F) Calculate HDD
Sunday 49 1 day (65-49)=16
Monday 47 1 day (65-47)=18
Tuesday 51 1 day (65-51)=14
Wednesday 60 1 day (65-60)=5
Thursday 65 1 day (65-65)=0
Friday 67 1 day (65-67)=0
Saturday 58 1 day (65-58)=7
Total 60 Degrees

This is equal to 60 degree days.