Building managers, owners, and residents typically try to maintain buildings at a comfortable interior temperature of 18°C. As outdoor temperature goes down, the amount of energy required for heating goes up. Similarly, as outdoor temperature goes up, the energy demand for most air conditioner and refrigeration systems increases. This indicator measures changes in the average annual energy requirements for heating and cooling of similarly constructed and insulated buildings from 1900 to 2013. Results are provided for British Columbia and each of the nine terrestrial ecoprovinces.

• Heating requirements decreased during the past century in British Columbia. Annual energy requirements for heating buildings in the province as a whole are decreasing by 600 Heating Degree Days (hereafter HDD) per century.
• The greatest reduction in heating requirements occur in the northern parts of B.C. In the Taiga Plains ecoprovince the anuual HDD has decreased by 670 HDD per century from 1900 to 2013. The Boreal Plains and Sub-Boreal Interior ecoprovinces experienced a decrease in HDD of 630 to 640 HDD per century.
• Cooling requirements increased across B.C. during the past century Annual energy requirements for cooling buildings in the province as a whole are increasing by 13 Cooling Degree Days (hereafter CDD) per century.
• The greatest increase in cooling requirements has been in the southern part of B.C. The Southern Interior ecoprovince has experienced an increase in annual CDD at a rate of 25 CDD per century.
• Energy requirements for heating and cooling buildings are related to average daily air temperature. The observed changes in energy requirements are consistent with observed increases in average annual air temperatures across B.C. In winter, less energy is required to keep buildings warm when average daily temperatures increase, as they have throughout B.C. over the last century.