A smart thermostat replaces the wall control for your heating and cooling system and adds Wi-Fi, an app and often voice assistant support. Before comparing features, check two things on every listing: whether your system is compatible and whether you need a C-wire, the common wire that supplies power.
The six models below cover buttons, round touchscreens and Matter support. Specs come from each product’s listing page, and where a listing contradicts itself we say so. We have not used these thermostats ourselves, and we make no claims about energy use or cost.
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What to Look For
| Feature | Why it matters |
|---|---|
| System compatibility | Check the maker’s compatibility checker for your HVAC type |
| C-wire | Some models need it; others include an extender kit or run on batteries |
| Control | Buttons, touchscreen, app or voice |
| Platforms | Alexa, Google Assistant, Apple Home, SmartThings and Matter |
| Extras | Remote room sensors, filter reminders and scheduling |
Specs at a Glance
| Thermostat | Display and size | Power | Works with |
|---|---|---|---|
| Sensi ST55 | LED display; 5.88 x 3.75 in; buttons | 24 VAC with 2 AA backup batteries | Alexa, HomeKit, Google, SmartThings |
| ecobee Essential | 3.74 in LCD touchscreen; round | Table says battery; listing mentions C-wire and extender kit | Alexa, HomeKit, Google |
| ecobee Enhanced | 4 in LCD; 4.09 x 4.09 in | 24 V wired; extender kit included | Alexa, HomeKit, Google, SmartThings |
| Honeywell Home X2S | LCD with buttons; Matter and Wi-Fi | C-wire required (24 VAC) | Alexa, Google, HomeKit, Matter |
| meross MTS300 | LED; 3.6 x 3.6 in | 24 V; C-wire required for some setups | Alexa, HomeKit, Google, SmartThings, Matter |
| Sensi Lite ST25 | LCD; 5.07 x 3.13 in | Battery or C-wire; 2 AAA included | Alexa, Google, SmartThings |
The 6 Best Smart Thermostats
1. Sensi ST55 Smart Thermostat
A button-style thermostat with a 5.88 by 3.75 inch body and an LED display, listed for furnaces, boilers, air conditioners and heat pumps. It works with Alexa, Apple HomeKit, Google Assistant and SmartThings, includes a built-in level and a filter indicator, and comes with 2 AA batteries and a 3-year warranty.
Suits: people who want buttons rather than a touchscreen. Strengths: broad platform support and a familiar layout. Weaknesses: the spec table lists button control while another row lists app, touch and voice. Skip it if you want a round touchscreen.
View Sensi ST55 Smart Thermostat on Amazon
2. ecobee Smart Thermostat Essential
A round 3.62 by 3.62 inch thermostat with a 3.74 inch touchscreen, auto-away, scheduling, fan control and eco+ features, working with Alexa, Google Assistant and Apple HomeKit. The listing says no C-wire is needed with the Power Extender Kit, sold separately, and the spec table lists the power source as battery, which does not match.
Suits: a compact touchscreen unit. Strengths: a touchscreen and optional SmartSensor support. Weaknesses: the extender kit is sold separately and the power rows conflict. Skip it if you want one wiring answer before you order.
View ecobee Smart Thermostat Essential on Amazon
3. ecobee Smart Thermostat Enhanced
A 4 by 4 inch wired thermostat with a 4 inch LCD, occupancy sensing, app control and a Power Extender Kit and trim plate in the box. It works with Alexa, Google Assistant, Apple HomeKit and SmartThings, and the listing states a 3-year warranty. SmartSensors are sold separately.
Suits: homes without a C-wire. Strengths: the extender kit and trim plate are included. Weaknesses: sensors cost extra. Skip it if you want Matter, which the listing does not mention.
View ecobee Smart Thermostat Enhanced on Amazon
4. Honeywell Home X2S Smart Wi-Fi Thermostat
A Matter-certified Wi-Fi thermostat with an LCD, app and button control, 7, 5-1-1 or 5-2 day programming, filter reminders and humidity monitoring. The listing supports up to 2 heat and 2 cool conventional systems and heat pumps with electric backup, and states that a C-wire is required.
Suits: a home that already has a C-wire. Strengths: Matter plus physical buttons. Weaknesses: a C-wire is required. Skip it if your wall has no common wire.
View Honeywell Home X2S Smart Wi-Fi Thermostat on Amazon
5. meross MTS300 Matter Smart Thermostat
A square 3.6 inch thermostat with an LED display, a glass panel in black or white, Matter support and 7×24 hour scheduling, working with Alexa, Apple Home, Google Assistant and SmartThings. The listing says some wiring setups require a C-wire, which is not included, and the control method row lists only voice.
Suits: a Matter smart home. Strengths: a small footprint and Matter. Weaknesses: a C-wire is needed in some setups. Skip it if you do not know your wiring.
View meross MTS300 Matter Smart Thermostat on Amazon
6. Sensi Lite ST25 Smart Thermostat
A simpler Sensi with an LCD, 5.07 by 3.13 inches, powered by batteries or a C-wire, with 2 AAA batteries included. It works with Alexa, Google Assistant and SmartThings, and the maker says some systems, such as heating-only, cooling-only and heat pump setups, may need a C-wire.
Suits: a basic smart thermostat with app control. Strengths: battery or C-wire power. Weaknesses: no HomeKit is listed. Skip it if you use Apple Home.
View Sensi Lite ST25 Smart Thermostat on Amazon
Care and Setup
- Turn off power to the HVAC system at the breaker before touching wires.
- Photograph the old wiring and label each wire before removing it.
- Run the maker’s compatibility checker first.
- Use a 2.4 GHz Wi-Fi connection if the listing asks for it.
Mistakes to Avoid
- Skipping the compatibility check.
- Assuming a C-wire is not needed.
- Choosing a model whose assistant support does not match your phone or speaker.
- Counting on maker claims about energy use as a guarantee.
Smart Thermostat FAQ
What is a C-wire?
The common wire carries constant low-voltage power to the thermostat. Several models here need it, and others offer a kit or batteries.
What does Matter mean?
Matter is a shared smart home standard. The Honeywell X2S and meross MTS300 list it.
The Short Version
For buttons, the Sensi ST55. For a compact touchscreen, the ecobee Essential. For a no C-wire kit in the box, the ecobee Enhanced. For Matter with buttons, the Honeywell X2S. For a small Matter unit, the meross. For a simple battery-or-wire model, the Sensi Lite.
