
Honeywell RTH9580WF
Score: 75/100
Emerson Sensi ST55
Score: 72/100Rankings

The Honeywell RTH9580WF delivers a sleek low-profile design, vibrant color touchscreen and Smart Response learning for precise temperature control. Its drawbacks include discontinuation, reliance on a C-wire and occasional Wi-Fi reliability issues. It suits tech-savvy homeowners who value aesthetics and learning algorithms but can manage potential support limitations.

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 | ![]() | ![]() |
|---|---|---|
1 years | 3 yearsbest | |
— | 5 inchbest | |
| ↓ lower better | 0.544 kg | 0.386 kgbest |
Click an attribute name to sort · Green = best, red = worst (relative to this comparison)
| Attribute | ![]() | ![]() |
|---|---|---|
General(2) | ||
HVAC Compatibility | Compatible with 24 V HVAC (forced air, hydronic, heat pump, oil, gas, electric); not compatible with millivolt or 120/240 V baseboard electric heat | Various (single to multi-stage) |
Warranty (years) | 1 years | 3 years |
Connectivity(2) | ||
Wi‑Fi Standard | 802.11b/g/n | 802.11 a/b/g/n (2.4GHz) |
Smart Home Integration | Alexa | Alexa, Google Assistant, Apple HomeKit, Samsung SmartThings |
Power & Installation(1) | ||
Power Source | 24 V | 20-30 VAC |
Display(1) | ||
Display Type | Capacitive touchscreen | LED touchscreen |
Features(1) | ||
Geofencing | false | true |
Build & Design(2) | ||
Device Weight (kg) | 0.5443 kg | 0.386 kg |
Device Dimensions (H×W×D) (mm) | 0.88x3.5x4.5 in mm | 25.4×149.35×95.25 mm mm |


Products in the top-left offer the best value (high score, low price).

Professional reviewers commend the Honeywell RTH9580WF for its ultra-slim profile, vibrant customizable touchscreen, and Smart Response learning that balances comfort with energy efficiency. Editors also note the ease of programming, integrated weather data, and ENERGY STAR rating as strong points, while flagging the product's discontinuation and limited sensor array as drawbacks.
Everyday users appreciate the intuitive touch interface, precise temperature control, and the convenience of remote app management, often citing the customizable display as a fun feature. Recurring complaints focus on Wi-Fi connectivity challenges, occasional app glitches, and the lack of automatic geofencing, with some expressing concern over the thermostat being discontinued.

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.
“Intuitive touch interface”

“Wi-Fi setup issues”


