Emerson Sensi ST55
Score: 72/100
Google Nest Learning Thermostat
Score: 87/100Rankings
The Nest Learning Thermostat 4th gen offers advanced learning algorithms, a large high-resolution touchscreen, and broad Matter and voice-assistant integration. Its premium price and single-zone limitation are notable trade-offs. Best suited for users who want a hands-off, feature-rich thermostat within the Google ecosystem.
Emerson Sensi ST55 provides a 5-inch LED touchscreen, broad smart-home compatibility, and geofencing-driven energy savings, all at an affordable price. Limitations include the need for a C-wire, 2.4 GHz-only Wi-Fi, and lack of built-in room sensors. Ideal for DIY homeowners seeking a versatile, budget-friendly thermostat.
| Attribute | | |
|---|---|---|
3 yearsbest | — | |
5 inchbest | 2.68 inch | |
| ↓ lower better | 0.386 kg | 0.162 kgbest |
Click an attribute name to sort · Green = best, red = worst (relative to this comparison)
| Attribute | | |
|---|---|---|
General(1) | ||
HVAC Compatibility | Various (single to multi-stage) | Up to 3 heating stages, 2 cooling stages, heat pump with auxiliary and emergency heat |
Connectivity(2) | ||
Wi‑Fi Standard | 802.11 a/b/g/n (2.4GHz) | 802.11n |
Smart Home Integration | Alexa, Google Assistant, Apple HomeKit, Samsung SmartThings | Matter, Google Home, Amazon Alexa |
Power & Installation(2) | ||
C‑Wire Requirement | true | false |
Power Source | 20-30 VAC | HVAC system wiring with rechargeable lithium battery |
Display(2) | ||
Display Type | LED touchscreen | Circular touchscreen |
Screen Size (inch) | 5 inch | 2.68 inch |
Build & Design(2) | ||
Device Weight (kg) | 0.386 kg | 0.162 kg |
Device Dimensions (H×W×D) (mm) | 25.4×149.35×95.25 mm mm | 3.9x3.9x1.1 mm |
Products in the top-left offer the best value (high score, low price).
Professional reviewers commend the Sensi ST55 for its straightforward DIY installation, ENERGY STAR efficiency and the claimed 23% energy savings, as well as its compliance with Title 24 and robust smart-home integration. However, they point out the need for a c-wire to unlock full functionality and the limitation to a 2.4 GHz Wi-Fi band.
Homeowners and renters alike praise the thermostat's quick setup, remote app control, energy-saving reports, and reliable fan circulation. Recurring complaints focus on occasional Wi-Fi drops, the necessity of a c-wire for some systems, and the lack of a built-in room sensor or precise humidity control.
Choose Nest if you want automatic learning and premium design and don't need HomeKit.
The Nest Learning Thermostat (4th gen) is Google's flagship smart thermostat featuring a 60% larger circular touchscreen, built-in machine-learning that auto-adjusts schedules, and seamless integration with Google Home, Matter, and Alexa for remote and voice control.
60% larger 2.7-inch circular touchscreen provides clearer readout from across the room; Dynamic Farsight automatically brightens the display for visibility and can be manually overridden; Built-in machine-learning adapts heating and cooling schedules to occupants' habits without manual programming; Auto-Away mode detects when the home is empty and adjusts temperature to save energy; Integrated Wi-Fi and Matter support enables remote control via Google Home app, voice assistants, and other smart-home ecosystems
