ecobee3 Smarter
Score: 84/100
Emerson Sensi ST55
Score: 72/100Rankings
The ecobee3 Smarter thermostat provides a 3.5-inch color touchscreen and a suite of built-in sensors for precise climate control, along with broad 24 V HVAC compatibility and optional Power Extender Kit. It requires a C-wire or additional kit and uses older 2.4 GHz Wi-Fi, which may limit some setups. Best suited for users wanting multi-zone sensing and Apple ecosystem integration.
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 | 3 yearsbest | |
3.5 inch | 5 inchbest | |
| ↓ lower better | 0.612 kg | 0.386 kgbest |
Click an attribute name to sort · Green = best, red = worst (relative to this comparison)
| Attribute | | |
|---|---|---|
General(1) | ||
HVAC Compatibility | ~95% of 24V systems (conventional 2H/2C, heat pump 4H/2C, gas/oil/electric/dual fuel, humidifier/dehumidifier/ventilator/HRV/ERV) | Various (single to multi-stage) |
Connectivity(3) | ||
Wi‑Fi Standard | 802.11 b/g/n (2.4 GHz) | 802.11 a/b/g/n (2.4GHz) |
Bluetooth Version | BLE 5.4 | BLE |
Smart Home Integration | Apple HomeKit, Amazon Alexa, Google Assistant | Alexa, Google Assistant, Apple HomeKit, Samsung SmartThings |
Power & Installation(1) | ||
Power Source | 24 VAC | 20-30 VAC |
Display(2) | ||
Display Type | color touchscreen | LED touchscreen |
Screen Size (inch) | 3.5 inch | 5 inch |
Build & Design(2) | ||
Device Weight (kg) | 0.612 kg | 0.386 kg |
Device Dimensions (H×W×D) (mm) | 23.6×100.3×100.3 mm 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 Ecobee3 for its comprehensive sensor suite that enables smart recovery and precise humidity management, as well as its extensive HVAC compatibility that covers most 24V systems. They note its value for multi-zone comfort without a hub, while pointing out the need for a C-wire or Power Extender Kit and the lack of newer Wi-Fi standards compared to later models.
Everyday users praise the thermostat for its straightforward installation and reliable Wi-Fi control, especially appreciating the seamless Siri and HomeKit integration. The most common feedback revolves around occasional wiring difficulties in homes without a C-wire, but overall sentiment is highly positive.
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.
“ease of install and Wi-Fi control”
“seamless Siri/HomeKit remote access”
