Cooling and heating degree days - Cities and FUAs by country
<p align="justify">This dataset provides indicators of Cooling and Heating Degree Days (CDDs and HDDs) for FUAs and cities. CDDs and HDDs are measurements used to estimate energy usage based on outdoor temperature. CDD measures the demand for cooling, while HDD measures the demand for heating, both calculated...
What the numbers show
Cooling and heating degree days - Cities and FUAs is currently reported for 2 countries. The highest value is 1,998 Degree days in Luxembourg; the lowest is 162.92 Degree days in Armenia.
The median across all reporting countries is 1,081 Degree days, and the mean is 1,081 Degree days.
The gap between the highest and lowest reporting country is a factor of about 12.
Cooling and heating degree days - Cities and FUAs: full country ranking
| # | Country | Latest | Year | 10-year change | Trend |
|---|---|---|---|---|---|
| 1 | Luxembourg | 1,998 Degree days | 2025 | down 10.9% | falling |
| 2 | Armenia | 162.92 Degree days | 2025 | down 1.1% | falling |
About this data
<p align="justify">This dataset provides indicators of Cooling and Heating Degree Days (CDDs and HDDs) for FUAs and cities. CDDs and HDDs are measurements used to estimate energy usage based on outdoor temperature. CDD measures the demand for cooling, while HDD measures the demand for heating, both calculated relative to a baseline temperature.</p> <h3>Data sources and methodology</h3> <p align="justify"> The indicators use 0.1-degree resolution grids from the <a href=https://developers.google.com/earth-engine/datasets/catalog/ECMWF_ERA5_LAND_DAILY_AGGR>ERA5-Land dataset</a>. ERA5-Land is used as it provides harmonised, globally consistent coverage at fine spatial resolution (0.1 degree), enabling the production of comparable subnational indicators also where national meteorological data are not available at the required scale. Annual CDDs are the sum over a year of the differences between the daily mean outdoor air temperature and the threshold temperature when the outdoor temperature is above the threshold temperature. HDDs are the sum over a year of the differences between the threshold temperature and the daily mean outdoor air temperature when the outdoor temperature is below the threshold temperature. Threshold temperatures are set to 22°C for CDDs and 15°C for HDDs.</p> <p align="justify"> These estimates may differ from official subnational climate statistics due to differences in methodological approaches, such as the use of reanalysis based top down modelling versus in situ observations, along with variations in input data sources, spatial resolution, and the models and algorithms used to generate temperature estimates. </p> <h3>Defining FUAs and cities</h3> <p align="justify">The OECD, in cooperation with the EU, has developed a harmonised <a href="https://www.oecd.org/en/data/datasets/oecd-definition-of-cities-and-functional-urban-areas.html">definition of functional urban areas</a> (FUAs) to capture the economic and functional reach of cities based on daily commuting patterns <a href=https://doi.org/10.1787/9789264174108-en>(OECD, 2012)</a>. FUAs consist of: <ol> <li><b>A city</b> – defined by urban centres in the degree of urbanisation, adapted to the closest local administrative units to define a city.</li> <li><b>A commuting zone</b> – including all local areas where at least 15% of employed residents work in the city.</li> </ol> The delineation process includes: <ul> <li>Assigning municipalities surrounded by a single FUA to that FUA.</li> <li>Excluding non-contiguous municipalities.</li> </ul> <p> The correspondence table between SAUs and FUAs/cities is available in <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.parquet>parquet </a> and <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.csv>csv</a> format. </p> The definition identifies 1 272 FUAs and 1 269 cities in all OECD member countries except Costa Rica and three accession countries.</p> <h3>Cite this dataset</h3> <p>OECD Regions, cities and local areas database (<a href="http://data-explorer.oecd.org/s/1dj">Cooling and heating degree days - Cities and FUAs</a>), <a href=http://oe.cd/geostats>http://oe.cd/geostats</a></p> <h3>Further information</h3> <ul> <li> <a href=https://localdataportal.oecd.org/>OECD Local Data Portal </a> </li> <li> <a href=https://www.oecd.org/en/publications/oecd-regions-and-cities-at-a-glance-2024_f42db3bf-en.html/>OECD Regions and Cities at a Glance </a> </li> </ul> <p align="justify">For questions and/or comments, please email <a href="mailto:CitiesStat@oecd.org">CitiesStat@oecd.org</a>