Degree Days

Degree days give a measure of the effect of the season's temperature on fuel requirements, especially in the case of a building which is continually heated.  For each day that the average temperature is one degree above the base temperature, one degree day has accumulated.

Probably the most widespread applications of the degree day concept is the management of industrial and domestic heating.  Heating degree days are indicators of household energy consumption for space heating. 

• The air temperature in a building is on average 2˚C to 3˚C higher than that of the air outside. 
• A temperature of 18˚C indoors corresponds to an outside temperature of about 15.5˚C. 
• If the air temperature outside is below 15.5˚C, then heating is required to maintain a temperature of about 18˚C. 

The sum of the degree days over periods such as a month or an entire heating season is used in calculating the amount of heating required for a building.  Degree Days are also used to estimate air conditioning usage during the warm season.

For further information please contact Met Eireann, Climate Enquiries Office Ph: 01 8064260 Fax: 01 8064216 or climate.enquiries@met.ie