Millivolt Thermostat for Gas Fireplace - Total Home Supply Millivolt Thermostats Designed for use with gas fireplaces and heaters, our millivolt thermostat options can be used with or without an external power source. We carry a variety of wired and wireless options to best suit your needs, including offerings from top brands such as Everwarm, Ambient Technologies and Empire Comfort Systems. Amazon: Gas Fireplace Thermostat 1-16 of 550 results for "Gas Fireplace Thermostat" Skip to main search results Amazon Prime. Eligible for Free Shipping. SkyTech TS-3 Wired Wall Mounted Thermostat Fireplace Control (SKY-TS-3) 3.7 out of 5 stars 21. $65 $ 65. 98. Get it as soon as Wed, Oct 9. FREE Shipping by Amazon.