THANKS! I tried everything here and nothing did work! This finally removed my no longer used entities without unique id. The best thing is that it actually is really simple and works on all my entities (it does not need to be an entity created with REST. For example it did work for my device_tracker entities which were once defined in my configuration.yaml).
Edit: Well, sadly it did not last a restart. After restarting all the entities are back there 
Backup. Always make backups.
If you donāt have a recent backup it is near impossible to recover the installation.
worked for me, thank!
For me, the entities were stored on various files under config/.storage. I just grep the name of the offending entity and edited the files with homeassistant down. Some files were json, so take care of deleting the entity while preserving the syntax.
Worked for me too : ) thank you (remember to refresh the browser otherwise it looks like it hasnāt workedā¦)
For me it worked like rahulpuk wrote:
Under āDevelper Tools - Servicesā key in āPurge Entitiesā. In the Dropdownmenue, select the entities/s you want to purge and hit Run. Then you need to do a reboot of the entire system (OS level, not just Developer Tools - Yaml - Reboot !).
After that, the orphaned entities are gone.
Worked for me as well! Thanks!