Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified
A budget-friendly smart thermostat that prioritizes privacy and traditional controls.
Full manufacturer title
Sensi Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified, ST55 DIY Thermostat
$95
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Ravvy verdict
89.7 / 100
Buy the Sensi ST55 if you want a reliable, easy-to-install smart thermostat that values privacy and simple operation over modern aesthetics.
- Best for
- homeowners with older wiring who prefer physical buttons over touchscreens
- Buy it if
- You want no C-wire required for most standard heating and cooling setups.
- Skip it if
- You are tech enthusiasts seeking color displays or sophisticated room-sensing technology.
- Best alternative
- Amazon Echo Dot (newest model) - Vibrant sounding speaker, Designed for Alexa+, Great for bedrooms, dining rooms and offices, Deep Sea Blue Deep Sea Blue Device only (Smart home beginners and eero mesh Wi-Fi users.)
How it scores on what matters
- Privacy98.0
- Installation Ease94.0
- Energy Efficiency89.0
- Connectivity85.5
- User Interface82.0
Ravvy factor scores, 0 to 100, derived from specs, owner reviews and category norms.
What it is
The Sensi ST55 is a refreshing alternative to the trend of oversized touchscreens and complex menu systems in the smart home space. It maintains the rectangular footprint and tactile physical buttons of a traditional thermostat, making it an excellent choice for those who want modern features without a steep learning curve. Despite its retro look, it is fully compatible with major voice assistants like Alexa and HomeKit, allowing for seamless integration into existing smart ecosystems. Installation is one of this units strongest suits, as it frequently bypasses the need for a C-wire in heat or cool only systems, a common hurdle in older homes. While the interface is simple, the underlying software provides robust energy reporting and maintenance alerts. It is a workhorse designed for reliability and data privacy rather than flashy aesthetics, ensuring your usage habits stay between you and your HVAC system.
Ravvy AI insight
The Sensi ST55 occupies a unique niche by offering Apple HomeKit compatibility at a sub-100 dollar price point, which is rare for budget models. While it lacks the advanced motion sensors of premium competitors, its ability to run on batteries for basic functionality makes it the safest bet for homes with unpredictable or antiquated HVAC wiring.
Generated from owner feedback, product specs, pricing, and retailer data. Last updated Aug 19, 2026.
What owners praise
- No C-wire required for most standard heating and cooling setups
- Physical buttons provide tactile feedback and ease of use
- Strict data privacy policy ensures user info is not sold
- Wide compatibility with Alexa, Google Home, and HomeKit
- Large footprint covers old screw holes and paint lines
What to know first
- Monochrome display feels dated compared to modern rivals
- Lacks geofencing capabilities found in higher-end models
- Requires a C-wire for Apple HomeKit connectivity
Specifications
- UPC
- 786710554827
- GTIN
- 786710554827
- Brand
- Sensi
- Color
- White
- Shape
- Rectangular
- Voltage
- 24 volts_of_alternating_current
- Brand Name
- Sensi
- Model Name
- ST55
- Unit Count
- 1 Count
- Screen Size
- 5 inches
- Control Type
- Button Control
- Display Type
- LED
- Finish Types
- Glossy
- Manufacturer
- Copeland
- Model Number
- ST55
- Power Source
- Corded Electric
- Material Type
- Plastic
- Mounting Type
- Wall Mount
- Product Style
- DIY
- Control Method
- App, Touch, Voice
- Item Type Name
- , Works with Alexa, Energy Star Certified
- Number of Items
- 1
- Special Feature
- Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable
- Product Dimensions
- 1"D x 5.88"W x 3.75"H
- Additional Features
- Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable
- Included Components
- Thermostat, free mobile app, 2 AA batteries, mounting hardware, wire stickers, installation guide, welcome guide with Sensi code, warranty booklet
- Number of Batteries
- 2 AA batteries required. (included)
- Connectivity Protocol
- Wi-Fi
- Connectivity Technology
- Wi-Fi
- Manufacturer Part Number
- ST55
- Temperature Control Type
- Programmable, Smart/Remote
- Item Dimensions D x W x H
- 1"D x 5.88"W x 3.75"H
- Specific Uses For Product
- Air Conditioner, Boiler, Furnace, Heat Pump
- Manufacturer Warranty Description
- 3 years.
- Global Trade Identification Number
- 00786710554827
How to get the most out of it
Check your C-wire early
While the Sensi works without a C-wire for most basic systems, smart features like HomeKit or continuous Wi-Fi connectivity are more stable when a C-wire is present. Check your wall before installation to see if a blue or black wire is tucked away.
Ownership tips
tip
Use the Sensi App for Setup
Avoid guessing which wires go where by using the Sensi mobile app during installation. It provides a custom wiring diagram based on your specific terminal labels, which prevents short-circuiting your transformer.
care
Monitor Battery Life
If you are not using a C-wire, the unit relies on two AA batteries. Change these annually to ensure your thermostat does not lose connection to your Wi-Fi network during extreme weather events.
Frequently asked questions
Does this thermostat require a C-wire?
For most standard heating and cooling systems, a C-wire is not required because the unit can run on batteries. However, a C-wire is mandatory for heat-only, cool-only, or heat pump systems, and it is recommended for a stable Wi-Fi connection.
Can I control this with my iPhone?
Yes, the Sensi ST55 is compatible with the Apple HomeKit ecosystem. You can use the Sensi app or the Apple Home app to adjust temperatures, though HomeKit functionality specifically requires a C-wire for power.
Will this help me save money on my electric bill?
As an Energy Star certified device, it provides features like scheduling and usage reports that help track your HVAC run time. Sensi claims users can save about 23 percent on their HVAC energy costs through efficient scheduling.
What happens if my Wi-Fi goes out?
If your internet connection drops, the thermostat will continue to operate based on the last saved schedule. You can always manually adjust the temperature using the physical buttons on the device itself.
Where can you buy the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified?
Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified is sold through Amazon, and Sensi also lists it through its own site and major retail partners. The buy link on this page goes straight to the current Amazon listing, which is where stock and pricing update most often.
How much does the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified cost?
The last price Ravvy recorded was $95. Retail pricing on smart home moves with promotions and stock, so treat that figure as a reference point and check the live listing before you buy.
How do you get the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified for a cheaper price?
Three tactics work best: watch for holiday and seasonal sale events when smart home discounts run deepest, compare the open box or renewed listing against new stock, and check whether Sensi is running a coupon or bundle. Adding the product to your Ravvy wishlist keeps it handy so you can revisit the listing when prices drop.
Is the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified in stock right now?
It was in stock at our last check. Availability on popular smart home can change within hours, so the live listing is the source of truth.
Is the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified worth it?
Ravvy scores it 89.7 out of 100. The strongest argument for it is no C-wire required for most standard heating and cooling setups. The trade off to weigh is monochrome display feels dated compared to modern rivals.
Who should buy the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified?
It fits homeowners with older wiring who prefer physical buttons over touchscreens If that does not describe your situation, compare it with the other options in Smart Home before committing.
What are the key specs of the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified?
UPC: 786710554827. ASIN: B01NB1OB0I. GTIN: 786710554827. Brand: Sensi.
What are good alternatives to the Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified?
Compare it against the other scored picks in Smart Home on Ravvy. We rank every option in that group by the same criteria, so you can see which model wins on value, quality, and owner sentiment before you decide.
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