Add Rehlko (formerly Kohler Energy Management) integration (#38782)

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: J. Nick Koston <nick+github@koston.org>

source/_integrations/rehlko.markdown

@@ -0,0 +1,54 @@
+---
+title: Rehlko
+description: Support for Rehlko devices (formerly Oncue and Kohler Energy)
+ha_category:
+  - Sensor
+ha_iot_class: Cloud Polling
+ha_release: 2025.5
+ha_config_flow: true
+ha_codeowners:
+  - '@bdraco'
+  - '@peterager'
+ha_dhcp: true
+ha_domain: rehlko
+ha_platforms:
+  - sensor
+ha_integration_type: integration
+---
+
+The **Rehlko** (formerly Kohler Energy Management) {% term integration %} allows you to monitor the status of your [enabled Kohler generator](https://www.kohlerhomeenergy.rehlko.com/kohler-energy-management-app) through Home Assistant. This integration replaces the legacy Oncue integration.
+
+{% include integrations/config_flow.md %}
+
+## Required manual input
+
+To configure a Rehlko (Kohler Energy Management) account, enter the following information:
+
+{% configuration_basic %}
+
+email:
+  description: "The email used to log in to the Rehlko (Kohler Energy Management) application."
+password:
+  description: "The password used to log in to the Rehlko (Kohler Energy Management) application."
+
+{% endconfiguration_basic %}
+
+## Sensor availability
+
+The sensors exposed by this integration depend on the specific instrumentation installed on your generator and transfer switch. Sensor availability can vary significantly—even between units of the same model.
+
+## Tested generators
+
+These are the generator models that have been tested:
+
+- [38RCLB](https://resources.kohler.com/power/kohler/residential/pdf/tp6908.pdf)
+- [20RESA](https://resources.kohler.com/power/kohler/residential/pdf/tp6804.pdf)
+- [20RCA](https://www.kohlerhomeenergy.rehlko.com/products/home+generators/20rca)
+- [14RESA](https://www.kohler.com/content/dam/kohler-com-NA/Lifestyle/PDF/PDF-tp6803.pdf)
+
+## Removing the integration
+
+This integration follows the standard integration removal process; no extra steps are required.
+
+{% include integrations/remove_device_service.md %}
+