diff --git a/Documentation/ProjectFile/prj/processes/process/HEAT_TRANSPORT_BHE/borehole_heat_exchangers/borehole_heat_exchanger/a_id.md b/Documentation/ProjectFile/prj/processes/process/HEAT_TRANSPORT_BHE/borehole_heat_exchangers/borehole_heat_exchanger/a_id.md
new file mode 100644
index 0000000000000000000000000000000000000000..0acac40a4e0acfed73356cff73089104bff68c6a
--- /dev/null
+++ b/Documentation/ProjectFile/prj/processes/process/HEAT_TRANSPORT_BHE/borehole_heat_exchangers/borehole_heat_exchanger/a_id.md
@@ -0,0 +1,7 @@
+The "id" is an optional parameter.
+It starts with 0, and is referring to different BHEs based on their "MaterialID".
+Then those BHEs will follow the configurations defined in this block.
+A mixed definition with and without id is not supported.
+If "id" is not given, then it will be set automatically with an ascending order, also starting from 0.
+With the "id" present, multiple BHEs can share the same configurations defined in a single block without repeating it.
+To specify the same definition for all BHE in the project, the notation id="*" can be used.
diff --git a/web/content/docs/processes/heat-transport/HEAT_TRANSPORT_BHE/index.md b/web/content/docs/processes/heat-transport/HEAT_TRANSPORT_BHE/index.md
index ac51da0c841f2de5ef830ae1b85b20f3170a0780..05d4775abda7fe68424427f3071c7db0804da3c0 100644
--- a/web/content/docs/processes/heat-transport/HEAT_TRANSPORT_BHE/index.md
+++ b/web/content/docs/processes/heat-transport/HEAT_TRANSPORT_BHE/index.md
@@ -50,8 +50,16 @@ In the configuration of `HEAT_TRANSPORT_BHE` process, it is generally configured
     <process_variable>temperature_soil</process_variable>
     <process_variable>temperature_BHE1</process_variable>
 </process_variables>
+<borehole_heat_exchangers>
+  <borehole_heat_exchanger>
+  </borehole_heat_exchanger>
+<borehole_heat_exchangers>
 ```
 
+The parameters of the BHE needs to be defined inside of `<borehole_heat_exchanger>` and were described in the following subsections. Multiple BHE can be simply defined by multiple `<borehole_heat_exchanger>` inside of `<borehole_heat_exchangers>`.
+
+To use one BHE definition for multiple BHE, the id notation from the medium is supported. If one BHE is specified by id, then all BHE definitions must belong to this convention. The following line `<borehole_heat_exchanger id="0,2">` specifies for example the same parameters for BHE 0 and 2. If all BHE are exactly the same, then `<borehole_heat_exchanger id="*">` can be used to set the parameters of one BHE definition for all BHE in the model.
+
 ### `<borehole>`
 
 The borehole `<length>` and `<diameter>` are defined here. The unit of these parameters are in $\mathrm{m}$. Here is an example of a borehole with 18 m in length and 0.13 m in diameter.