Why is the fuel saving shown in the project report more than the amount of solar energy (solar energy in MWh) transferred to the storage tank?

The fuel saving is the energetic saving divided by the fuel heating value Hi (lower heating value) or Hs (higher heating value), depending on which of these values has been set for the boiler (auxiliary heating) efficiency. The energetic saving is not the same as the amount of energy transferred to the system (e.g. to the storage tank), but is calculated for each step of the simulation from solar energy in relation to the boiler efficiency. (NB: If the solar system would not be present, the boiler would have to deliver the calculated amount of solar energy at the corresponding efficiency.) The boiler efficiency values are given in the boiler dialog. If you carry out a calculation without space heating the software uses the efficiency for domestic hot water supply.
The help facility in the programme has the following definition for fuel savings: The available solar energy is converted, using the respective auxiliary heating efficiency, to give the corresponding primary energy equivalent.

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