Degree Days

Tom Meyer

Degree Days = 65 - (high + low)/2

"Degree Days" are defined as the difference between the average temperature and the 65 deg F reference temperature.

Senior Designer/Trainer
Precision Hydronics Corporation
www.precisionhydronics.com

David Smith

Heating Days

Do any of you "old timer" remember what the fomrula is to figure heating degree days ? I guess I'm getting old and forgetfull.
Thanks for the help



David

Steve Ebels

Data

If you're looking for degree day data, go to accuweather.com. They have current as well as historical numbers for the whole U.S. Great website for weather hounds and us heating/cooling types.

Alan R. Mercurio

A degree day is simply a unit of measuring how cold (or hot) it has been over a 24 hour period. Whenever the average, (or mean) temperature is below 65°, you have a degree day. For example, if in a 24 hour period the high outside temperature was 70° and the low was 50°, then the average temperature for that day was 60° - halfway between 70° and 50°. This is 5 degrees less than the base temperature of 65°. Therefore we can say that there was 5 degree days for the period.

Along with the degree days, there is what is called a K-Factor. A K-Factor is simply a number for showing how fast a customer uses fuel. Once the K-Factor is established for a given customer, it is multiplied by the usable gallons of fuel in the customer's tank to find how many degree days can elapse between deliveries.
By keeping track of how many degree days have accumulated, you have a system for knowing just when to deliver fuel to any individual customer. . . maximizing your deliveries and your profits.


Your friend in the industry,

Alan R. Mercurio

Oil Tech Talk

Larry_7

Degree Day Hourly

I think DD calcs based on hourly averages is substantially more accurate when attempting to compare DD's to consumption. A little more work is involved, though. There is a reliable site that gives avg temps for major cities and these are averaged hourly and divided by 24 to give the daily avg. I set up a spreadsheet to calculate the heating and cooling DD based on daily avg input. Occasionally they miss a day or so for lack of data but I've found other sites that give the hourly data and I have to avg for the 24 hr period before entering into my spreadsheet. A bit of a drag but worth the better accuracy. If interested try www.engr.udayton.edu/weather/citylistUS.htm

I used this setup to convince myself that our first Munchkin consumed over 30% less fuel than the beast we replaced. We now sing the Muchkin song to anyone who will listen.

Larry