ecobee Smart Thermostat Premium with SmartSensor vs Sensi Smart Thermostat ST55
These are side-by-side facts taken from each product guide: published specifications, strengths and caveats as their sources state them. This page is not a test, a ranking or a verdict about which model is better.
ecobee Smart Thermostat Premium with SmartSensor
24 VAC forced-air, heat pump, boiler or PTAC systems, checked first with ecobee's compatibility tool
ecobee's top thermostat ships with a room SmartSensor, the Power Extender Kit and a trim plate. The maker's spec sheet covers conventional 2H/2C, heat pumps to 4H/2C, boilers and PTACs on 24 VAC, and rules out line-voltage, millivolt and 0-10VDC systems. Dual-band Wi-Fi, Alexa built in, Siri with an Apple home hub. Read the warranty's installer clause before you fit it yourself.
Published specifications
- Maker: 24 VAC systems; conventional 2H/2C; heat pump 4H/2C; boilers; PTAC or fan coil to 3 fan speeds
- Maker: not compatible with line voltage (110/220V), millivolt or 0-10VDC systems
- Maker: Power Extender Kit included for homes without a C wire; booklet requires 3 or 4 specific wires
- Maker: dual-band Wi-Fi 2.4GHz and 5GHz, Bluetooth 5.0, 915MHz sensor radio, 4 VA, hardwired
- Maker: 4.09 x 4.09 x 1.02 in; 4-inch 540x540 touchscreen; trim plate and one SmartSensor in the box
- Warranty: 3-year limited; maker's pro sheet advertises 5 years with professional installation
Strengths
- SmartSensor, Power Extender Kit and trim plate are all included, not add-ons
- Maker publishes a full spec sheet: stages supported, wire terminals, Wi-Fi bands and power draw
- Dual-band Wi-Fi, Alexa built in, Siri with an Apple home hub, Google Assistant and SmartThings
Caveats
- The warranty excludes units not installed by a licensed HVAC contractor, while the listing sells DIY installation
- The Power Extender Kit only works if you have the three or four wires the booklet names
- Listing paperwork is inconsistent: part number EB-STATE6-01 and a user guide warranting a different ecobee model
Read the full ecobee Smart Thermostat Premium with SmartSensor guide
Sensi Smart Thermostat ST55
Conventional or heat pump systems up to two stages, on a 2.4GHz network, in the old thermostat's footprint
A button-and-LED smart thermostat whose manual configures one or two stages of conventional cooling, gas or electric heat, and one or two stage heat pumps, with a built-in RC/RH jumper you clip for two-transformer systems. Batteries are included, but the manual says a common wire is required on heat-only, cool-only and heat pump systems.
Published specifications
- Manual: terminals RH, RC, C, Y, Y2, W/E, W2, G, O/B and a non-functional L
- Manual: configures AC1/AC2 cooling, GA1/GA2 gas, EL1/EL2 electric, HP1/HP2 heat pump, fan-only and no-cooling
- Manual: common connection required on heat-only, cool-only or heat pump systems; listing says C wire not needed in most applications
- Manual: two-transformer systems supported by clipping the internal RC/RH jumper above the battery compartment
- Manual: Sensi app and Sensi account required to install; router must be a 2.4GHz network
- Warranty: three-year retail limited warranty; five years only for PRO models installed by a PRO contractor
Strengths
- Handles two-stage heat and two-stage cool, heat pumps and two-transformer systems at an entry price
- Fits the old thermostat's footprint with buttons, a built-in level, wire labels and AA batteries in the box
- Both the installation guide and the full warranty text are published on the listing itself
Caveats
- The manual requires a common wire on heat-only, cool-only and heat pump systems, and no adapter is included
- 2.4GHz Wi-Fi only, and the Sensi app plus a Sensi account are required to install it at all
- Warranty remedy is replacement only, is void if you attempt a repair, and excludes commercial installations
How to choose between them
Choose the ecobee Smart Thermostat Premium with SmartSensor if your situation matches: 24 VAC forced-air, heat pump, boiler or PTAC systems, checked first with ecobee's compatibility tool. Its main caveat: The warranty excludes units not installed by a licensed HVAC contractor, while the listing sells DIY installation.
Choose the Sensi Smart Thermostat ST55 if your situation matches: Conventional or heat pump systems up to two stages, on a 2.4GHz network, in the old thermostat's footprint. Its main caveat: The manual requires a common wire on heat-only, cool-only and heat pump systems, and no adapter is included.
Both entries repeat what each guide records. Confirm the model, included parts and availability on the current listing before ordering.
Primary sources
- ecobee Smart Thermostat Premium tech specs and sell sheet (maker PDF) Source for ecobee Smart Thermostat Premium with SmartSensor
- ecobee product page for Smart Thermostat Premium Source for ecobee Smart Thermostat Premium with SmartSensor
- ecobee installation booklet supplied with the Amazon listing Source for ecobee Smart Thermostat Premium with SmartSensor
- ecobee terminal-designation chart supplied with the Amazon listing Source for ecobee Smart Thermostat Premium with SmartSensor
- ecobee user guide supplied with the Amazon listing Source for ecobee Smart Thermostat Premium with SmartSensor
- Sensi Wi-Fi Programmable Thermostat installation guide supplied with the Amazon listing (Emerson) Source for Sensi Smart Thermostat ST55
- Emerson Thermostat Limited Warranty supplied with the Amazon listing Source for Sensi Smart Thermostat ST55
- Sensi (Copeland) manuals index for the Sensi smart thermostat Source for Sensi Smart Thermostat ST55
Primary sources checked .