diff --git a/source/_integrations/modbus.markdown b/source/_integrations/modbus.markdown
index 4506ebdcce1..97c15c39e65 100644
--- a/source/_integrations/modbus.markdown
+++ b/source/_integrations/modbus.markdown
@@ -756,6 +756,25 @@ climates:
               description: "Value corresponding to Fan Diffuse mode."
               required: false
               type: integer
+    hvac_onoff_register:
+      description: "Address of On/Off state.
+        When the value defined by `hvac_off_value` is read from this register, the HVAC
+        state is set to Off. Otherwise, the `hvac_mode_register` dictates the state
+        of the HVAC. If no such register is defined, it defaults to Auto.
+        When the HVAC mode is set to Off, the value defined by `hvac_off_value` is written to
+        the register, otherwise the value defined by `hvac_on_value` is written."
+      required: false
+      type: integer
+    hvac_on_value:
+      description: "The value that will be written to the `hvac_onoff_register` to turn the HVAC system on.
+        If not specified, the default value is 1."
+      required: false
+      type: integer
+    hvac_off_value:
+      description: "The value that will be written to the `hvac_onoff_register` to turn the HVAC system off.
+        If not specified, the default value is 0."
+      required: false
+      type: integer
     swing_mode_register:
       description: "Configuration of the register for swing mode"
       required: false