= 55 HDD). HDD means Heating Degree Day. Wednesday, September 5, 2007
Duke Energy -- For Upcoming Winter
Magic Formula: Victorian House heating 3300 sq. ft. During Winter, divide HDD for the day by 3 and that's your cost for natural gas. On a really cold day with HDD @, say, 55, cost will be $18. HDD of 55 is an average temperature of 10 degrees. (65 degrees less 10 degrees 
= 55 HDD). HDD means Heating Degree Day.
= 55 HDD). HDD means Heating Degree Day.