Which helper sensor for mapping data from other sensors?

[Roemer (Roman)]

Hello all
I am in the process of creating helpers for a lot of my Entities.
The basic idea is that I have a stable entity (the helper) for some kind of data, regardless if the data the helper gets the data from changes in the future.

For example:

• I have a zigbee template sensor in the garden shed. This is an entity that is added via mqtt. Now it is very probable that I will replace that sensor with another one within the next 1-2 years. This would lead to a data loss of the old data when I use a new sensor. So I will create a helper “temperature-shed” and for now, use the entity from mqtt to fill its value and when I replace the sensor, just adjust the “temperatur-shed” helper to the new sensor entity.
• Same goes for a lot of other things like energy monitoring, where the devices change often.

So my question is: What helper type should I use?

• Template which is not as easy to create but provides a lot of freedom
• Group helper which is easy to use (just select the single entity I need)
• Min/Max helper
• Any other?

Many thanks for your tips regarding this. My goal is to have a set of stable sensors which can keep all data even when I replace the hardware that provides the value.

[WallyR (Wally)]

Dont use device ids.
Use entity ids and problem is solved with a rensning.

Why and how to avoid device_ids in automations and scripts

Background When you start writing automations, a device trigger seems the obvious choice. Everybody knows what a device is and it comes at the top of the UI dropdown list. [image] It works… but it is certainly not a “great way to start” because it is storing up problems for the future. Far better to use an entity, with state or numeric_state. This topic is part of the community-driven cookbook where you can find other topics you might be interested in or might like to contribute to. Devi…

[Roemer (Roman)]

But let’s say I would use “sensor.temperature-shed” as entitiy-id for the current sensor. If I then add a new one, it needs to be named differently as the other id is already used. could I just rename the old one and then also rename the new one? Does this keep the history and statistics data?

[WallyR (Wally)]

It keeps the history connected to the entity id.
If you change the entity id, then it is. New sensor with a new history.
If you change it back, then it is the old sensor again and it continues the history.

[parautenbach (Pieter Rautenbach)]

Adding new devices and replacing devices

The biggest favour you can do yourself is to rename entities to a functional name when you add new devices. Let’s say if you’ve added a new device, such as a smart switch to control a light and monitor its power. Let’s also say that the integration that allows you to add it to Home Assistant provides you with a technical entity ID such as switch.shelly_1pm_2f4dee. You should rename this to (for example) switch.living_room_lamp, which describes its purpose. Doing this will ensure that should yo…

[Roemer (Roman)]

Thanks for the link. Seems like this topic is a rabbit hole. There are up/downsides for different approates or the “alias” idea. I personally think the most flexible approach would be to use template helpers. This would allow to cover pretty much every scenario. Even for example a scenario where a new “device” would not expose the temperature as an entity but as an attribute and such things.

[parautenbach (Pieter Rautenbach)]

What you want to do is a lot more work, but I won’t/can’t stop you from doing that.

What’s suggested is quite simple: Use entity IDs, not device IDs. Name entities appropriately (this is your stable entity now). When you replace a device, remove the old entities and rename the new ones to the old names.