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WEDNESDAY JANUARY 3 - HEATING DEGREE DAYS
One measure used by energy companies to estimate customer consumption during the cold
months is called "Heating Degree Days". The concept of "Heating Degree Days" is based
on the assumption that people will start to heat their homes when the average daily
temperature drops below 65oF.
Now, "Heading Degree Days" is actually sort of a confusing term, because each day that
the average temperature drops below 65 has its own number of "heating degree days".
Here's what I mean.
Let's say that on a particular day, the high temperature is 48 and
the low is 32. The average for the day is thus 48+32 divided by 2, or 40. Subtract this
average from 65 to get the number of heating degree days for that day - in this case,
25. Energy companies do this calculation for each day on which the average temperature
goes below 65, and then add all the numbers together, to get the total heating degree
days for the year. That total helps them compare and allocate the energy needs of
In most cases, consumers will find a very good correlation between heating degree
days and heating costs. Check this National Weather Service web page for daily and
monthly calculations of heating degree days: