What are Heating Degree Days?

[JEDI]

Heating Degree Days (weather derivatives / insurance index converting temperature into prices)

on my gas bill, it has hdd and therms.

hdd = 668, therms = 66

Therms is easy. it's the amount of gas used.

What's the purpose of hdd?

 

[FoBoT]

Degree Days, Heating (HDD): A measure of how cold a location is over a period of time relative to a base temperature, most commonly specified as 65 degrees Fahrenheit. The measure is computed for each day by subtracting the average of the day's high and low temperatures from the base temperature (65 degrees), with negative values set equal to zero. Each day's heating degree days are summed to create a heating degree?day measure for a specified reference period. Heating degree days are used in energy analysis as an indicator of space heating energy requirements or use.

they put it on there to give you an idea of why your bill went up, if the HDD were the same as last year but your bill went up, then maybe something is wrong with your furnace or insulation. but if the HDD changed and your bill changed, then that is due to temperature differences

 

[Strk]

I've never heard of the hdd, but your therms are five fewer than mine

 

[iamwiz82]

A heating degree is the difference between the current temperature and 65F, assuming the temp. is below 65F. If it is above 65F, it's a cooling degree.

Add up the heating days in a month and you have HDD.

 

[JEDI]

Originally posted by: iamwiz82
A heating degree is the difference between the current temperature and 65F, assuming the temp. is below 65F. If it is above 65F, it's a cooling degree.

Add up the heating days in a month and you have HDD.

so how come my hdd=668 if there are only 30days in a month?!

 

[iamwiz82]

Originally posted by: JEDI

Originally posted by: iamwiz82
A heating degree is the difference between the current temperature and 65F, assuming the temp. is below 65F. If it is above 65F, it's a cooling degree.

Add up the heating days in a month and you have HDD.

so how come my hdd=668 if there are only 30days in a month?!

668 degrees below 65 over the course of a month.

 

[FoBoT]

668 divided by 30 = 22.3
so that month averaged 22.3F below 65F, some days may have been 30F below 65F and some 10F below 65F , etc etc , the total degrees for the 30 days = 668