Archive:Heating and cooling degree days - statistics
Data extracted in December 2020.
Planned article update: May 2021.
Highlights
The use of indicators or indexes such as Heating degree days (HDD) and Cooling degree days (CDD) can contribute to the correct interpretation of energy consumption for cooling and heating buildings. Heating degree days (HDD) and cooling degree days (CDD) are weather-based technical indexes designed to describe the energy requirements of buildings in terms of heating (HDD) or cooling (CDD). This article aims to present the variations of HDD and CDD since 1979, that we have data availability.
Full article
Cooling and heating degree days by country
Higher heating degree day values in Sweden and Finland
Heating degree days (HDD) varies across European countries. Considering all data available over the 1979-2020 period, Finland had the highest average annual HDD value (5 665). For Malta, the value of this index was 536. This means that for a given building, the need for heating was ten times less important in Malta than in Finland between 1979 and 2020 (see Figure 1). Finland was followed by Sweden (with an average HDD of 5 328) and Estonia (4 344) (see Figure 1). The European countries with the lowest HDD were Malta (536), followed by Cyprus (784) and Portugal (1 243).
Considering the latest year under observation (2020), the countries with the highest HDD values were Finland (4 871), Sweden (4 593) and Estonia (3 553) (see Figure 2). This means that in 2020, a given building would have greater needs for heating in Finland, Sweden and Estonia compared to the rest of Europe, because of lower temperatures (below 15°C) were more frequent. The countries with the lowest HDD values for 2020 were Malta (402), Cyprus (630) and Portugal (1 008).
The correlations between the countries annual heating degree day data are available in table 2. They are organized in increasing arithmetic average value order. On the correlation analysis, neighboring countries have higher heating degree days values. Countries of similar latitude have similar arithmetic average values but if their longitude is different, the correlation varies.
Higher cooling degree days in Cyprus and Malta
Similar to heating, cooling degree days (CDD) varies across Europe. Figure 3 shows the annual averages across 42 years, from 1979 to 2020. Cyprus has the highest CDD (573), followed by Malta (569) and Greece (268). The lowest values for this index were calculated for Ireland (CDD=0.02), Sweden (0.36) and Denmark (0.91). This means that for a given building, the need for cooling (or air conditioning) in Ireland, Sweden and Denmark were negligible between 1979 and 2020.
Considering the latest year under observation (2020), the countries with the highest values were Cyprus (803), Malta (672) and Greece (345) (see Figure 4). This means that in 2020, a given building would have greater needs for cooling (or air conditioning) in Cyprus, Malta and Greece compared to the rest of Europe, because higher temperatures (over 24°C) were more frequent. The lowest CDD index calculated were for Ireland (0.00), Sweden (0.08) and in Finland (0.42) in 2020. The correlations between the countries annual cooling degree day data are available in table 3. They are organized in increasing arithmetic average value order. On the correlation analysis, neighboring countries have higher heating degree days values. Countries of similar latitude have similar arithmetic average values but if their longitude is different, the correlation varies.
Table 4 here
When looking into individual monthly HDD values and CDD, the highest value ever observed for a HDD was in January 1985 in Finland (1 198) and the highest value ever observed for a CDD was in August 2010 in Cyprus (269).
Cooling and heating degree day by NUTS 3 regions
NUTS 1 regions classification based on their average HDD values
On NUTS 1 regional level, table 3 classifies the regions in increasing HDD values. As expected, Canarias (ES7), Região Autónoma da Madeira (PT3), Malta (MT0), Kypros (CY0) and Nisia Aigaiou, Kriti (EL4) regions have the lowest average HDD values. It is interesting to observe that other regions/Member States, geographically distant have similar average values, such as Makroregion Poludniowo-Zachodni (PL5), Slovensko (SK0) and Bayern (DE2). Éire/Ireland (IE0) has similar average values with Grand Est (FRF) and Alföld és Észak (HU3). The same applies to Lietuva (LT0), Westösterreich (AT3) and Östra Sverige (SE1).
Table 5 NUTS1 here
NUTS 1 regions classification based on their average CDD values
On NUTS 1 regional level, table 3 classifies the regions in increasing CDD values. Éire/Ireland (IE0), Norra Sverige (SE3), Åland (FI2), Södra Sverige (SE2) and Danmark (DK0) regions have the lowest average CDD values. It is interesting to observe that other regions/Member States, geographically distant have similar average values, such as Makroregion Województwo Mazowieckie (PL9), Cesko (CZ0) and Zuid-Nederland (NL4). The same applies to Noroeste (ES1), Hessen (DE7) and Région de Bruxelles-Capitale/Brussels Hoofdstedelijk Gewest (BE1), as well as to Közép-Magyarország (HU1), Provence-Alpes-Côte d'Azur (FRL) and Yugozapadna i yuzhna tsentralna Bulgaria (BG4).
Table 6. NUTS 1 here
Cooling and heating degree day by NUTS 3 regions
Higher HDD values in Norrbottens län and Lappi regions
On regional level, the annual averages for all available data spanning across 41 years, from 1979 to 2020 show that Norrbottens län region in Sweden had the highest HDD value (6660). The lowest value was observed in Fuerteventura, Spain (HDD=18). In 2020, in Lappi, Finland the highest HDD value measured was 5 965. The lowest was in Fuerteventura, Spain with 0,57.
Higher cooling degree days values in Malta and Cyprus
At regional levels, the annual averages for all available data spanning across 42 years, from 1979 to 2020 showed that Gozo and Comino / Ghawdex u Kemmuna region in Malta had the highest CDD value (583). The second country where, for a given building, the need for cooling (or air conditioning) was significant is Cyprus (CDD=573). In 2020, the highest cooling degree days value was measured in Cyprus (803).
Cooling and heating degree days at EU27 level
Heating Degree Day values are decreasing in time
The HDD value decreased by 21% between 1979 and 2020 indicating that 2020 only 79% of the heating needs occurred as compared to 1979. The arithmetic average across 41 years of data is 3 209. From the measurements we have, the trend shows that heating degree days are decreasing across time. With the exception of a four years (2010, 2005, 2004 and 2001) heating degree days are lower than the average after 1999.
Cooling Degree Day values are increasing in time
In contrast, the CDD values 2020 was more than two times higher between 1979 (37) and 2020 (99), indicating that the needs for cooling (air conditioning) in a given building increased over the last decades. For cooling degree days, the trend we observe from our measurements shows an increase across time. The average CDD for EU27 value is 72. After 2001, only a few years (2002, 2004, 2005 and 2014) are below the average.
Source data for tables and graphs
Context
Over the last decades, the effects of global warming caused relevant impacts in many sectors. Given the previsions, this tendency is expected to persist at least until the end of this century. Identifying climate-related impacts and assessing how important these impacts are is an important element of any effective strategy for managing future climate risks. Weather-related energy consumption for heating and cooling buildings indicators such as HDD and CDD can contribute to monitor energy demand for cooling and heating buildings under climate change.
Methodology
Heating degree day (HDD) index is a weather-based technical index designed to describe the need for the heating energy requirements of buildings. Cooling degree day (CDD) index is a weather-based technical index designed to describe the need for the cooling (air-conditioning) requirements of buildings. We derive HDD and CDD data from meteorological observations of air temperature, interpolated to regular grids at 25 km resolution for Europe. We aggregate calculated gridded HDD and CDD and we present them on NUTS-3 level.
Heating Degree Days (HDD) index: the severity of the cold in a specific time period taking into consideration outdoor temperature and average room temperature (in other words the need for heating). The calculation of HDD relies on the base temperature, defined as the lowest daily mean air temperature not leading to indoor heating. The value of the base temperature depends in principle on several factors associated with the building and the surrounding environment. By using a general climatological approach, the base temperature is set to a constant value of 15°C in the HDD calculation. If Tm ≤ 15°C Then [HDD = ∑i(18°C - Tim)] Else [HDD = 0] where Tim is the mean air temperature of day i. Examples: If the daily mean air temperature is 12°C, for that day the value of the HDD index is 6 (18°C-12°C). If the daily mean air temperature is 16°C, for that day the HDD index is 0.
Cooling degree days (CDD) index: the severity of the heat in a specific time period taking into consideration outdoor temperature and average room temperature (in other words the need for cooling). The calculation of CDD relies on the base temperature, defined as the highest daily mean air temperature not leading to indoor cooling. The value of the base temperature depends in principle on several factors associated with the building and the surrounding environment. By using a general climatological approach, the base temperature is set to a constant value of 24°C in the CDD calculation. If Tm ≥ 24°C Then [CDD = ∑iTim - 21°C)], Else [CDD = 0] where Tim is the mean air temperature of day i. Examples: If the daily mean air temperature is 26°C, for that day the value of the CDD index is 5 (26°C-21°C). If the daily mean air temperature is 22°C, for that day the CDD index is 0.
These calculations are executed on a daily basis, added up to a calendar month and subsequently to calendar years. Annual data are calculated as sum of monthly data by Eurostat.
Data sources
This dataset includes monthly data as published by the Joint Research Centre's AGRI4CAST Resources Portal [1] . Note that Eurostat is not the producer of the monthly data, but is only re-publishing them.
Direct access to
Database
- Energy (nrg), see:
Cooling and heating degree days by country - annual data (nrg_chdd_a)
Cooling and heating degree days by country - monthly data (nrg_chdd_m) Cooling and heating degree days by NUTS 3 regions - annual data (nrg_chddr2_a) Cooling and heating degree days by NUTS 3 regions - monthly data (nrg_chddr2_m)
Dedicated section
Methodology
- Energy statistics - cooling and heating degree days (ESMS metadata file — nrg_chdd)