SAP 2005 Online Calculation of Annual Solar Contribution

The Valentin Energy Software Online Calculation based on the United Kingdom Government's Standard Assessment Procedure (SAP) for Energy Rating of Dwellings (2005 Edition)

The following calculation provides a theoretical annual thermal energy yield figure generated from a typical solar domestic hot water system (SDHW) fitted in the UK. This figure is used as part of a longer assessment within the ‘Standard Assessment Procedure’ (SAP) which is intended to provide the UK government with an average estimate of energy of a whole house which is independent of geographical location as well as individual hot water patterns. SAP also provides a general basis to report carbon dioxide mitigation.

The resulting figure on this site is intended as a comparative guide and should be checked against the published manual method before using this to complete a full SAP calculation. The calculated figure shown here should not be used alone as indicative solar performance as other factors will be required in SAP for the complete analysis of the DHW system. For example pump electrical losses and back-up appliance efficiency are not considered here.

The calculated SAP figure for solar DHW will have reduced accuracy in the following cases:

For a more complete analysis of a solar heating system, the T*SOL range of solar simulation software is available now in the following free demo versions:

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The numeric references shown below (Hx) are equivalent to those found in Appendix H of SAP. The calculated result (Line H17) is automatically calculated when the boxes are completed. If you require further clarification of the terminology and units used for the SAP calculation, you are recommended to read Appendix H of the SAP document which can be viewed here.


  Collector type
  Tilt of collector
  Orientation of collector
  Over-shading factor
(H1) Indicate the Aperture area of solar collector, m²
    If only the collector overall (gross) area can be established, enter this and tick this box
(H2) Indicate a different value for the Zero-loss collector efficiency, η0, only if taken from an EN 12975 test certificate
(H3) Indicate a different value for the Collector heat loss coefficient, a1, only if taken from an EN 12975 test certificate
Total floor area (m²)
This determines the daily DHW energy and distribution losses needed to calculate Solar-to-load ratio
Select this if there is a combi boiler used for back-up DHW
(H9) Select this if there is no cylinder thermostat controlling a boiler

(H11) Dedicated solar storage volume, Vs, litres
Volume of the solar heat storage not normally heated by other heat sources:
    Either a) enter the entire volume of a separate pre-heat cylinder and leave H12 blank
b) Enter the volume of the lower solar part of a combined cylinder and complete box H12
(H12) Factor for combined cylinders
    Either a) leave blank for separate pre-heat cylinders
b) enter a figure in litres for the total combined volume of the store

The following result (H17) gives a figure that is entered into line 50 of the main SAP worksheet

SAP Calculation Result:

The Solar Design Company is Valentin Energy Software’s partner
in the United Kingdom.

Please contact The Solar Design Company if you require technical
support for the Valentin SAP 2005 Online Calculation of Annual
Solar Contribution.