Degree-days: Comparison of calculation methods

Abstract

The uncertainties associated with calculating degrees-days from traditional formulae and other approximate methods were examined. Comparisons were based on calculations using hourly temperature records. A definition of uncertainty for monthly degree-days and some typical errors in annual values are presented. The ranges of uncertainty are small for published degree-days, but could be significant for a small percentage of occasions. If the methods are used for base temperatures lower than the current standard then the uncertainties increase. Also shown are the effects of these errors on the regression analysis often used in building energy monitoring.