Weather adjustment

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The heating energy consumption is influenced from year to year by different climatic conditions.

In order to be able to compare the heating energy consumption of different years or different locations, the energy consumption must be adjusted for the weather . For this purpose, the degree day figures of a comparison period are put in relation and a climate correction factor ( GTZ reference year / GTZ year ) is determined.

There are two procedures for this in Germany:

  • According to the old VDI 3807 Part 1 (1994), the heating limit temperature and the internal temperature were each assumed to be 15 ° C
  • According to VDI 2067 Part 1, the interior room temperature is 20 ° C and the heating limit temperature is 15 ° C; this is also used again in VDI 3807 Part 1 (2013) and the Energy Saving Ordinance 2007.

For long-term comparisons, VDI 3807 (2013) uses the mean value for the years 1961–1990 from Würzburg , this degree day number is 3883 Kd / a .

Application example

After a renovation measure, the heating energy consumption is still 75% of the previous year's consumption. The number of degree days for the previous year was 3200 Kd / a and is now 3000 Kd / a. The correction factor is calculated with 3200/3000 = 1.066. The actual energy consumption is therefore probably a little higher, namely 75% multiplied by the correction factor of 1.066 = 80%. This results in a weather-adjusted saving of only 20% instead of the actually measured 25% after the renovation.

Now the heating energy consumption at the location is to be standardized for Germany in a consumption-based energy certificate in order to enable a nationwide comparison. The reference value for this is 3767 (Potsdam, test reference year TRY11). The correction factor is therefore 3767/3000 = 1.256, with which the actual consumption must be applied.

Web links

  • German Weather Service - climate correction factors, current and recent years
  • Degree days in Germany , Institut für Wohnen, Darmstadt (xls table, also includes the average values ​​per weather station and is constantly updated)

Individual evidence

  1. ↑ IWU: Degree day numbers in Germany, explanations in xls file. Retrieved April 20, 2016 .