« All thermostats

Lennox S40 Smart Thermostat

Thermostats

The ultimate controller for more precise comfort

Rating

Price Guide

$$$$

Warranty

10-Year Limited Warranty

View Full Product Specifications

Features

Ratings & Reviews

See what other customers are saying about
Lennox S40 Smart Thermostat

5/5

Happy Buyer

March 02, 2025

I purchased the S-40 a month ago with a new heat-pump system and back-up gas furnace for my home in Northern Utah. I find the S-40 to be user-friendly both when using the thermostat and the app on my iPhone and it has all of the features I need. That said, my needs are pretty simple, unlike some of the other reviewers. There was an initial issue with the thermostat displaying a temperature consistently 3 to 4 degrees higher than the actual temperature right in front of the unit. At first that issue stumped my HVAC company, but after some research they found there was a display temperature calibration adjustment in the advanced settings (plus or minus 5 degrees). Once that was adjusted it tracks the temperature accurately. I also appreciate the true variable capacity of my heat pump and furnace, so, while the S-40 is very expensive, getting the full functionality from the heat-pump and furnace was important to me and worth it. My home is a noticeably more comfortable with the temperature being more consistent without the wide swings of my old one-stage furnace. I also appreciate the 10 year warranty given how expensive the S-40 is to replace.