Energy / Heating / Cooling index or degree days

Degree days is a measure of how weather-dependent energy use for period of interest differs from the normal (i.e. the long-term average). It is typically used for weather normalization but is also useful for identifying periods with certain energy use patterns (for example periods with normal, low, or high energy use). An energy index is calculated like heating degree days, but additionally accounts for insolation and wind-driven infiltration by converting these weather effect into centigrade equivalents. For example, setting the solar factor to 0.01 adds 1°C to the outdoor temperature when the global horizontal irradiance is 100 kW/m2 (i.e. 0.01 °C*m2/ kW * 100 kW/m2 = 1 °C). Thus, setting the solar and infiltrations factors to 0 results in ordinary heating/cooling degree days.
Average values, calculated per selected aggregation, are denotes with an ‘_avg’-suffix. You should select at least 10 years of data to get 'normal' degree days.

This feature is experimental and might change in the future.

The plot is linked to the table, thus all filtering and odering affects the plot as well.

Note: x-axis shows local standard time. However, some browsers will erroneously label it as UTC time zone in the tooltip shown on mouseover events

Data sources

The ERA5 reanalysis dataset provides hourly estimates of a large number of climate variables. ERA5 data provided by this website is stored in a format for optimized for fast time series access on a regular lat/lon grid of 0.25/0.25 degrees, between -56 and 71 latitude degrees and only for non-ocean grids. Only variables relevant for energy modelling are provided, do let me know if you think more variables should be included.

The CAMS radiation service provides time series of radiation parameters. The geographical coverage is the field-of-view of the Meteosat satellite, roughly -66° to 66° in both latitudes and longitudes.


lukas.rokka [at]

Updated 2021-04-04