Q: Integrating SAGA 7.8.1 into QGIS 3.16 (OS Windows 10) I want to calculate the PV potential of roofing using QGIS, similar to this post:
How to calculate total PV potential of a roof using QGIS?.
However, my SAGA version in QGIS does not show me the Potential Incoming Solar Radiation algorithm.
I have downloaded a standalone SAGA version 7.8.1.
Can I integrate the latest/ update the current SAGA version that is used by my QGIS?
The OS I am using is Windows 10.
I am completely new to SAGA in QGIS and have no previous experience in using it.

A: SAGA 7.8 comes with saga4qgis and it provides support for SAGA Algorithms through QGIS Processing Toolbox.
This is a short instruction to install saga4qgis into QGIS 3.16, on Windows10 environment.
(1) Download latest SAGA
Visit SAGA in SorceForge.net, and download the latest zipped version of SAGA (i.e. saga-7.8.2_x64.zip).

(2) Unzip downloaded SAGA and search for saga4qgis.zip file.

(3) Unzip saga4qgis.zip

You will find two files and a folder.

*

*readme.txt: This is the instruction (see below).

*SagaNameDecorator.py

*description (folder with lots of description files)

Open readme.txt - it is short and sweet
Replace the SAGA binaries in:
> C:\Program Files\QGIS X.Y\apps\saga(-ltr)

Adjust the interface in:
> C:\Program Files\QGIS X.Y\apps\qgis(-ltr)\python\plugins\processing\algs\saga(-ltr)

Adjust version in file:
> SagaAlgorithmProvider.py
>> REQUIRED_VERSION = '7.7.'

(4) Folow the instruction as written in readme.txt.
That's it - below is my note but it has no additional information.

*

*Open up [aa] C:\Program Files\QGIS 3.16\apps\saga-ltr folder and delete all files inside it.

*Copy all files of unzipped saga-7.8.2_x64.zip to the above folder [aa].

*Open up [bb] C:\Program Files\QGIS 3.16\ apps\ qgis\ python\ plugins\ processing\ algs\ saga and search for SagaNameDecorator.py file. Replace this file by new SagaNameDecorator.py (which is in saga4qgis.zip).

*In the same [bb] folder, find SagaAlgorithmProvide.py and open it by a text editor (e.g. Notepad++). Change REQUIRED_VERSION = '2.3.' to REQUIRED_VERSION = '7.7.'.

*You will find description folder in the same [bb] folder. Delete all files in this [bb]\description folder, and copy all description files in saga4qgis\description into this.

*Start QGIS 3.16 and examine QGIS Processing Toolbox.


