ISO 15927-6:2007 specifies the definition, method of computation and method of presentation of data on accumulated temperature differences, used for assessing the energy used for space heating in buildings. These are normally expressed in degree‑hours or degree-days, and such data are often referred to simply as "heating degree-hours" or "heating degree-days".
ISO 15927-6:2007 includes approximate methods for calculating accumulated temperature differences based on hourly or daily mean temperatures and for estimating monthly values to any base temperature, for use when data computed directly from meteorological air temperature records are not available.
In some countries, a threshold temperature different from the base temperature is used. ISO 15927-6:2007 does not cover this.