Updated Jul 18, 2018

Emerson Sensi vs. Nest Gen 3: Only One Is HomeKit Compatible

Cam Secore

After a month of testing, I determined Nest Gen 3 is the best smart thermostat because of its brilliant design and ability to save you money effortlessly. Emerson Sensi is a solid option if you want control via HomeKit, but you’ll need to manually set up geofencing and Home app automation to save money on your heating and cooling.

I’ll compare and contrast two smart thermostats (Emerson Sensi vs. Nest Gen 3) by evaluating five categories: software, setup, operation, design, and price.


Nest Learning (Gen 3)

  • Software: It learns patterns, making it easy to save money without thinking about it.
  • Setup: The app guides you through the whole seamless process.
  • Operation: Nest will work with 95% of HVAC systems, you don’t need the c-wire, and it always stays online.
  • Design: It looks fantastic and feels even better. Nothing matches its craftsmanship.
  • Price: The third generation is $250, while Nest E is $170.

Best for you if...

You want to save money on your heating and cooling without thinking about it or tinkering with the settings. Nest features brilliant software, setup, and design. Everything about this product is perfectly thought out. The two concerns with Nest are its price ($250) and lack of HomeKit support. But if Nest is doing all of the temperature customizations for you, do you need to use the Home app?


Emerson Sensi Wi-Fi

  • Software: It’s HomeKit compatible, but there isn’t much in the way of automatic smarts.
  • Setup: Installation was easy through the phone app.
  • Operation: It doesn’t require the c-wire because it uses two AA batteries, but this is unreliable.
  • Design: It looks like a traditional thermostat and isn’t aesthetically appealing.
  • Price: The entry-level Sensi is $90, while Sensi Touch is $150.

Best for you if...

You want an affordable smart thermostat, and you’re an iPhone user with a c-wire. You can save with Sensi, but you’ll need to tinker with your settings (i.e., set schedules and geofencing). Don’t get Sensi unless you have a c-wire or you’re okay with your thermostat being offline because of the replaceable batteries. While you can control it with Siri, Ecobee is a higher quality HomeKit option.

Nest Gen 3


Software (A):

  • Nest is the smartest thermostat on the market. Conserving energy and saving money is easier than ever with this device.
    • It goes into “Eco Mode” when you’re not home by using a combination of the sensor on the thermostat and your phone’s location (geofencing).
    • It recognizes patterns. Do you turn down the heat before going to bed? Nest will start doing it on its own after you do it manually a couple of times.
    • If you have a static schedule and come home at the same time every day, Nest will adjust the temperature before you get home so that it reaches your desired temperature before opening the door.
    • AirWave feature keeps your fan running for 5-10 minutes after the AC compressor stops running, which essentially gives you “free AC” because there’s still cool air in the coils.
  • Nest’s phone app is well designed, and it integrates well if you have other Nest products.
  • My only beef with Nest’s software is that it isn’t HomeKit compatible. This doesn’t mean can’t use it as an Apple user, just that it doesn’t work with the Home app, Siri, and you can’t run automation.

Setup (A+):

  • Installation is seamless. The app guides you through the whole process. Nest even comes with a fancy screwdriver. It’d be hard to screw anything up. If you install the wires incorrectly, Nest is smart enough to troubleshoot on its own and find a solution.

Operation (A+):

  • Nest will work with 95% of HVAC systems, and you don’t need the c-wire (check compatibility).
  • The power difference between Nest and Sensi, is that Nest has a rechargeable battery, so you don’t need to swap out batteries. It should work at all times.

Design (A+):

  • Nest looks fantastic and feels even better. I’ve tested six smart thermostats, and there’s nothing that compares with Nest’s craftsmanship.
  • It comes in four colors.
  • You can customize the screen to look however you like. The display can show the current temperature, the outside temperature, or show the desired temperature.
  • It’s not a touchscreen, you spin the dial to navigate menus, and push in to click. It’s similar to old-school iPods’ click wheel.

Price (F):

  • The third generation Nest is $250, while the more affordable version Nest E (same as Nest 3, but with an uglier design and no FarSight display) is $170.

Emerson Sensi


Software (C+):

  • The phone app is surprisingly solid. You can use it for scheduling, and it allows you to lock the keypad from your phone so roommates, children or tenants can’t change the settings without your permission.
  • Sensi is HomeKit compatible, meaning you can control it from your iPhone’s control panel, the Home app or with Siri. (You need c-wire for this).
  • The Sensi app has geofencing features.
  • If you have a HomeKit hub (iPad, HomePod, Apple TV), you can set up geofencing with automations in the Home app. Geofencing works better with the Home app if you have multiple people in your household with iPhones because they don’t need to install the Sensi app for it to work.
  • You can offset the temperature if you think it’s incorrect.
  • I wasn’t expecting to see onscreen weather and humidity conditions like Nest and Ecobee, but Sensi provides it.
  • Unlike Nest, it has no “learning” features.
  • There are no in-depth usage reports.

Setup (B):

  • Installation was easy. Make sure you download the app first, and it’ll walk you through the process. You’ll get lost if you follow the paper instructions.
  • Sensi’s online guides for setup, frequently asked questions, and troubleshooting steps are great.

Operation (D):

  • This thermostat does NOT require the c-wire because it uses two AA batteries to stay powered (check compatibility). That’s great, but if you’re not using the c-wire, you’ll have issues because the Sensi isn’t getting constant power. Sometimes it will be offline, and you won’t be able to control it from your phone.
  • You have to replace batteries.
  • There’s no alert for low battery. If you’re not using the c-wire and it runs out juice, you’ll have serious problems.
  • Sensi doesn’t work as a humidistat replacement.
  • Sensi relies on its cloud servers rather than an internal web server.

Design (D):

  • Sensi looks like a traditional thermostat and isn’t aesthetically appealing. But this makes it accessible to people who want WiFi features on their thermostat but are intimidated by the “fancy” looking WiFi devices.
  • The backlight is too bright during the night, and there’s no way to change that. It’s either on or off.
  • I looked at the original Sensi, but if you prefer a nicer looking design, check out Sensi Touch.

Price (A+):