Emerson Sensi Smart Thermostat - ST55U

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Sensi Smart Thermostat (tested with st55u) can only be used with the app if you give your information such as location and phone, and enable internet to the product.

Emerson Sensi Smart Thermostat - ST55U

Basic Information
Release Year	2014
Product Type	thermostat, Software
In Production	Yes
Official Website	https://sensi.copeland.com/en-us/shop/st55

Consumer-impact summary

User Privacy

One can use the product fully disconnected from the internet without the Sensi app. If one wants to use the app, once adding the device to the app, the app will force the user to register it. the registration requires the following information:

• Precise address where the product resides (can be manually typed and works even with non existing locations)
• Contractor phone number (optional)
• Device has to be connected to the internet to talk to the Sensi APIs for the registration

The registration cannot be skipped if one wants to use the thermostat with the sensi app. this means that the thermostat will have to ping the sensi servers to be used with the app.

Furthermore, say you have decided to allow internet connection to the thermostat for the registration aspect, if you decide to disable internet access from your router to the thermostat, the app will show it as offline and you wont be able to control it anymore, even within local network.

Usage without letting the device see leave the local network

The thermostat is apple home enabled, if one has an iphone, they can connect the device using the sensi app which will ask if one wants the device to use apple home. Once connected to apple home, the user will be able to turn it on and off even if the device was not registered within the Sensi app. additionally if the thermostat is connected to a network that does not provide access to the internet, then the device will still work with apple home locally.^{[citation needed]}

Drawbacks of this method is that the user cannot benefit from using the thermostat with its full list of features that includes scheduling and geofencing to name a few.

Interesting notes:

The product manual states that it wants to let the consumer control their tools, but if one does not enable internet they cannot use the sensi app...

(Will be expand upon with more information and pictures)

Concerns

During testing, when disabling internet to the thermostat from the router, while in local network, the Sensi app can still communicate with the thermostat and change its status for roughly 10 more seconds.^{[citation needed]} It appears to be that while the thermostat didn't notify the app that it is offline, the app will think it is online and be able to communicate with it on the local network.^{[citation needed]} proving this is a forced limitation by the Sensi developers. The real concern is, if the house losses internet but still has electricity then the app will not work.

Note that the apple home option still works. and since its apple home compatible there might be good ways to integrate the thermostat with home assistant (untested)

References

https://sensi.copeland.com/en-us/shop/st55 - Archived Link (Snapshot Date: Mar 2 2026)

https://www.energystar.gov/productfinder/product/certified-connected-thermostats/details/2406365 - Archived Link (Snapshot Date: Oct 12 2025)