When comparing iDevices Thermostat vs ecobee3, the Slant community recommends ecobee3 for most people. In the question“What are the best HomeKit thermostats?” ecobee3 is ranked 1st while iDevices Thermostat is ranked 5th. The most important reason people chose ecobee3 is:
The display shows the current temperature, as well as which mode you're in (off, auto, cooling or heating), as well as humidity and the current weather. There is also a temperature slider handy for quick adjustments.
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Pros
Pro Affordable price for a basic HomeKit thermostat.
This thermostat is priced about $100 cheaper than any other option that currently integrates with HomeKit. For users who don't want/wouldn't use any fancy features but just want great Siri integration, this thermostat will suffice and at a more wallet-friendly price.
Pro More features in the works
While this thermostat is very feature-light at the moment, Bluetooth hardware is present which will allow for more features in the future. Geo-fencing and pattern recognition software are two features currently in development, however the other thermostats already offer these features and more.
Pro Important information is displayed at a glance
The display shows the current temperature, as well as which mode you're in (off, auto, cooling or heating), as well as humidity and the current weather. There is also a temperature slider handy for quick adjustments.
Pro Satellite sensor provides extended sensing range
Instead of a single point of sensing which can be influenced based on its location, the ecobee3 also utilizes a satellite sensor. This satellite sensor provides another perspective on the house, and between the two will provide smarter heating and cooling.
For example, if the main thermostat is located near a heat source (kitchen, full living room, etc) or cold source (near a door in winter) it can be influenced by temporary temperature fluctuations. The satellite sensor can help detect these temporary changes, and won't over-heat (or over-cool) the house when it isn't actually required.
The range on this extra sensor is about 45 feet, which should be plenty for most houses.
Pro Full web support allows monitoring and adjusting from anywhere
In addition to the phone app, you can access the web portal for (almost) full control of the system. This is very handy if your phone's battery dies, as you can login from any internet connected device.
Pro Integrates with numerous other systems
In addition to HomeKit, the ecobee3 can hook up with IFTTT (IF This Then That - an automation tool based on custom recopies), Alexa (Amazon's voice activated personal assistant found in it's Echo line of products), Wink (a stand-alone ecosystem) as well as SmartThings (Samsung's smart home ecosystem). This allows integration with a wider variety of smart home products outside of the HomeKit ecosystem.
Pro Straightforward install for 5 wire systems
If you already have the common wire (ie your system uses 5 wires), the installation is very quick and easy.
Cons
Con Multiple touches required for simple actions
Because the screen is so small and pixelated, very little can be displayed on the screen at one time. This forces the menus to be longer, which requires more button presses to scroll down and then select the action, and then finally adjust it. It would also be helpful if text was used instead of just icons, as then you'd never have to guess what an icon represents.
Con Lacks any standout features
As of right now (future updates could change this), the iDevices thermostat doesn't provide any compelling reason to choose it over any other HomeKit thermostat. It doesn't add any features of its own - instead it only has features provided by HomeKit itself which are present on many other thermostats. The screen is small and pixelated, and it still uses buttons instead of a touchscreen. It also looks more like a standard thermostat than the others.
Overall, the iDevices thermostat may be the cheapest option, but it's very uninspiring.
Con Installation is harder than it should be
Wiring the iDevices Thermostat requires a small precision screw driver (not included), and unlike many other smart thermostats it doesn't automatically detect which HVAC system you have (you will need to look that up, whether it's gas or electric fired, and potentially what kind of pumps and valves are used). The whole installation process is a lot more involved than other smart thermostats.
Con Installation can be tricky for 4 wire systems
If your system lacks the common (C) wire and is only a 4 wire system, you will need to use the included Power Extender Kit (5-wire systems don't require this). Then, additional steps are required depending if your HVAC system has a controller board or not.
Con Extra satellite sensors cost extra
One satellite sensor is included in the box, but if you want more you'll have to buy them. They come in packs of 2, and are sold at $79. It would also be convenient if you could buy just 1 additional sensor as well, but packs of 2 seem to be the only way they come.
Con The external sensor can lose connection
The satellite sensor is handy, but it adds another connection point which can disconnect (and based on user reviews, it can do so frequently even when installed within 5 meters of the main thermostat).