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Lennox S40 Smart Thermostat

Thermostats

The ultimate controller for more precise comfort

NO PAYMENTS UNTIL 2023

and rebates up to $1,200

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Warranty

10-Year Limited Warranty

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Features

Ratings & Reviews

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Lennox S40 Smart Thermostat

5/5

Easy to use

January 21, 2026

Holds the house at the perfect temperature. Works with my fully communicating EL19KPV and CBK48MVT. Super intuitive and easy to use.

Jeff W

Everett Washington

Age: 35 to 44

Gender: Male

Reason for Replacement: Planned

Features:

5/5

January 04, 2026

4/5

Lighted view

November 23, 2025

The only problem is the screen. The white of the numbers are too small to see properly across the room. It’s predecessor was easily viewed no matter what the light in the room is

JanP

Warranty Satisfaction:

4/5

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Product Specifications

Feature

Lennox S40 Smart Thermostat

Rating

System Compatibility

Works with premium Lennox® communicating equipment only AND pairs with Lennox Smart Accessories (Smart Room Sensors, Smart Air Quality Monitor and Wireless Extender)

Amazon Alexa

Allows you to voice control your HVAC system through Amazon Alexa-enabled devices

Amazon Alexa

Allows you to voice control your HVAC system through Amazon Alexa-enabled devices

Google Assistant

Allows you to voice control your HVAC system through Google Assistant-compatible devices

Google Assistant

Allows you to voice control your HVAC system through Google Assistant-compatible devices

Programmable

Versatile programming options offer custom comfort and energy savings

Programmable

Versatile programming options offer custom comfort and energy savings

Smooth Setback Recovery

Senses extreme temperature changes and begins the temperature recovery process up to 2 hours before the programmed time

Smooth Setback Recovery

Senses extreme temperature changes and begins the temperature recovery process up to 2 hours before the programmed time

Smart Away

Uses the GPS in your smartphone to detect when you're leaving, and automatically changes the temperature to a more energy-efficient setting

Smart Away

Uses the GPS in your smartphone to detect when you're leaving, and automatically changes the temperature to a more energy-efficient setting

Schedule IQ

Allows you to only program your thermostat once. Whenever there's a change in your routine, the thermostat adapts heating and cooling to match

Schedule IQ

Allows you to only program your thermostat once. Whenever there's a change in your routine, the thermostat adapts heating and cooling to match

One-Touch Away Mode

Overrides your regular programming schedule when you're away and automatically turns down heating or cooling to save energy

One-Touch Away Mode

Overrides your regular programming schedule when you're away and automatically turns down heating or cooling to save energy

Allergen Defender

Monitors the air quality and pollen levels of your local zip code and automatically turns the fan on to clean your home\u2019s air when outdoor levels are high

Allergen Defender

Monitors the air quality and pollen levels of your local zip code and automatically turns the fan on to clean your home\u2019s air when outdoor levels are high

Feels Like

Similar to the \"Feels Like\" temperature in a weather report, this feature takes into account temperature and humidity to create a comfortable environment

Feels Like

Similar to the \"Feels Like\" temperature in a weather report, this feature takes into account temperature and humidity to create a comfortable environment

Filter Reminder

Reminds you when its time to change the filter

Filter Reminder

Reminds you when its time to change the filter

Auto Changeover

Decides between heating and cooling operation, depending on indoor temperature

Auto Changeover

Decides between heating and cooling operation, depending on indoor temperature

Touchscreen

Features a large, easy-to-use display with adjustable brightness

Touchscreen

Features a large, easy-to-use display with adjustable brightness

Photo Display

Allows you to display a personal photo as the screensaver of your thermostat

Photo Display

Allows you to display a personal photo as the screensaver of your thermostat

Weather Screen Savers

Themed screen savers on the 7\" HD color touchscreen are designed with graphics that tell you what weather conditions are like outside

Weather Screen Savers

Themed screen savers on the 7\" HD color touchscreen are designed with graphics that tell you what weather conditions are like outside

Dual-Fuel Capability

Increases the efficiency of dual-fuel heating systems by automatically alternating between gas and electric operation

Dual-Fuel Capability

Increases the efficiency of dual-fuel heating systems by automatically alternating between gas and electric operation

Energy Reports

Show how often and how long the heating or cooling system has run for the month

Energy Reports

Show how often and how long the heating or cooling system has run for the month

Humidity Control

Works with the whole-house humidity-control systems to adjust the home's humidity level

Humidity Control

Works with the whole-house humidity-control systems to adjust the home's humidity level

Remote Capability

Monitor and adjust temperatures and schedules from anywhere in the world using the iComfort App and your smartphone, tablet or other web-enabled device

Remote Capability

Monitor and adjust temperatures and schedules from anywhere in the world using the iComfort App and your smartphone, tablet or other web-enabled device

Precise Comfort® Plus

Holds your home's temperature to within 0.5 degree or less when used with premium Lennox\u00ae equipment

Precise Comfort® Plus

Holds your home's temperature to within 0.5 degree or less when used with premium Lennox\u00ae equipment

Emailed Alerts

Provides detailed diagnostics and reminds your Dealer when service is needed

Emailed Alerts

Provides detailed diagnostics and reminds your Dealer when service is needed

Remote Monitoring

Allows Lennox dealers to analyze your system from anywhere via their computer or mobile device

Remote Monitoring

Allows Lennox dealers to analyze your system from anywhere via their computer or mobile device

Remote Troubleshooting

Makes it possible for dealers to use their mobile device to adjust system parameters to fix problems, without ever making a trip to your home

Remote Troubleshooting

Makes it possible for dealers to use their mobile device to adjust system parameters to fix problems, without ever making a trip to your home

Warranty

10-Year Limited Warranty

Lennox S40 Smart Thermostat

Thermostats

The ultimate controller for more precise comfort

Our Lennox Dealers are here to help

Features

Ratings & Reviews

Easy to use

Lighted view

Get answers from a Lennox® Dealer.

Get the answers you need from your preferred dealer:

AZ Air Cond & Heating

Find a Lennox dealer near you

Get answers from a Lennox^® Dealer.