Reference

Degree-Day Calculation Method

So you decide you want to do a degree-day analysis (or have someone like kWIQly do one for you). - What does it involve - the calculations are not the problem !


Update February 2012 : You can now get degree-days for anywhere on the planet calculated for free by kWIQly


Given a stream of dry-bulb temperatures (normal Celsius or Fahrenheit ignoring wind-chill) - We can write down how we calculate heating degree-days for any particular balance-temperature really easily:


Instructions ...


For each regular temperature measurement in a day write down 0 if
temperature is above balance-temperature. Otherwise write down the difference between balance-temperature and air-temperature. Degree days is the average of all the numbers written down.


Here is a really simple worked example....



Time Air Temperature Degree-Load for 15.5 Balance
12:00 AM 12 3.5
01:00 AM 9 6.5
02:00 AM 8 7.5
03:00 AM 8 7.5
04:00 AM 7 8.5
05:00 AM 6 9.5
06:00 AM 5 10.5
07:00 AM 4.5 11
08:00 AM 6 9.5
09:00 AM 7 8.5
10:00 AM 8 7.5
11:00 AM 12 3.5
12:00 PM 15 0.5
01:00 PM 16.5 0
02:00 PM 15.5 0
03:00 PM 14 1.5
04:00 PM 13 2.5
05:00 PM 12.5 3
06:00 PM 11 4.5
07:00 PM 10 5.5
08:00 PM 10.5 5
09:00 PM 9 6.5
10:00 PM 8 7.5
11:00 PM 8.5 7

Average 5.71

So here we see a day with 5.71 "Degree-Days" of load - It is simply the area in "degree-days" under the horizontal balance temperature line - Shown here in Red - The lower the Temperature (Green)  - The bigger the red area relative to the balance or "on-set of heating" line