Google Nest Thermostat (Charcoal) 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.
Google Nest Thermostat (Charcoal)
Single-stage 24V systems that need a schedule and app control, not multi-stage equipment
Google's entry thermostat: a 2.4-inch touch-bar disc powered from HVAC wiring with two AAA backup cells. Google lists one stage of heating and cooling plus a second stage of one or the other, or a heat pump with aux or emergency heat. Matter certified, works with Hey Google and Alexa. The trim plate and the steel plate are both sold separately.
Published specifications
- Maker: most 24V systems; one stage heat and cool plus a second stage of either; heat pump with aux or emergency heat
- Maker: works with multi-zone systems but needs one thermostat per zone
- Maker: designed to work without a C wire; heating-only, cooling-only or zone-controlled systems may need one
- Maker: primary power from HVAC wires, backup 2 x AAA 1.5V; under 1 kWh a month
- Maker: Wi-Fi 2.4 GHz and 5 GHz plus Bluetooth LE; Matter certified; Hey Google and Alexa voice control
- Maker: 3.3 in diameter, 1.07 in deep, 4.9 oz; 2.4-inch 240x320 display; 1-year standard warranty
Strengths
- Works without a C wire in most homes, on either 2.4 GHz or 5 GHz Wi-Fi
- Matter certified with Hey Google and Alexa voice control, and a published one-year warranty that matches the listing
- Built-in motion sensing turns it down when nobody is home, with schedule suggestions in the app
Caveats
- Only one extra stage: no two-stage heat plus two-stage cooling, and no multi-stage heat pump support
- Trim plate and steel plate are both sold separately, and the steel plate is required on an electrical box
- Setup needs the Google Home app and a Google account, and the listing states there is no lock feature
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 Google Nest Thermostat (Charcoal) if your situation matches: Single-stage 24V systems that need a schedule and app control, not multi-stage equipment. Its main caveat: Only one extra stage: no two-stage heat plus two-stage cooling, and no multi-stage heat pump support.
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
- Google Store tech specs for Nest Thermostat Source for Google Nest Thermostat (Charcoal)
- Google Nest Thermostat setup sheet supplied with the Amazon listing, with the box contents Source for Google Nest Thermostat (Charcoal)
- Google Nest Thermostat welcome guide supplied with the Amazon listing Source for Google Nest Thermostat (Charcoal)
- 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 .