A thermostat is the central component of all heating and cooling systems that lets you control the room’s temperature or adjust the system’s output to different parts of the day. So, in this article, we’re going to show you how to find the best millivolt thermostat that will enable you to control millivolt systems.
These devices are fairly simple, as they often lack advanced options offered by thermostats for low-voltage or line-voltage systems. Consequently, units designed specifically for millivolt systems are incompatible with standard furnaces or 4-ton heat pumps.
Our guide to finding the best millivolt thermostats will take you through the most important features of these devices and hopefully provide you with the information to help you choose the right model for your furnace.
Check out our guide to the fireplace systems for more information about how gas fireplaces work.
The 5 Best Millivolt Thermostats
| Model | Dimensions | Warranty | Price range |
| Honeywell CT53K1006 | 2.8 x 6.3 x 9 inches | 1-year, 30-day money-back guarantee | $ |
| Orbit 83521 | 1.3 x 5.3 x 3.25 inches | 1-year limited warranty | $$ |
| Emerson White-Rogers 1F80-0224 | 6.3 x 4.41 x 1.73 inches | 5-year warranty | $$$ |
| Lux Products TX9600TS | 5.38 x 1.13 x 3.38 inches | 3-year limited warranty | $$$ |
| Braeburn BRA 1220 | 3.70 x 5.16 x 1.38 inches | 5-year warranty | $$ |
This Standard Heat and Cool Non-Programmable Thermostat is easy to install and even easier to use with its lever control and clearly marked modes.
Understanding millivolt systems
Millivolt thermostats are designed to control the so-called millivolt heating systems. Furnaces that don’t run on electricity are at the core of these systems. So, the easiest way to find out if you have a millivolt heating system is to check its power source.
It is worth pointing out that nearly 90% of households in the United States utilizes low voltage heating solutions such as heat pumps or standard gas furnaces. Unfortunately, you cannot control these heating systems with millivolt thermostats because they commonly use electronic ignition.
The most common type of millivolt systems are:
- Direct and top-vent wall furnaces
- Floor heaters
- Gas fireplace furnace
- Tankless water heaters
- Gravity furnaces
- Direct-vent furnaces for mobile homes
These systems are outdated, as several regulatory bodies are working on legislation that prohibits their use in modern buildings. Hence, the chances are that you won’t need a millivolt thermostat unless you live in an old apartment block or if you have a gas-powered fireplace.
Go through our guide to furnace types to learn more about the differences between single-stage and dual-stage furnaces.
The main components of a millivolt thermostat
Unlike other types of thermostats, a millivolt thermostat doesn’t need an external electrical source to operate normally. Instead, it can draw energy from batteries or a thermopile that converts thermal energy into electricity.
They feature just two wires that enable you to connect the device to the furnace, and they’re usually only compatible with heating systems. Depending on the model, these devices may or may not have a display that shows you the furnace’s current temperature.
However, recent models have dual compatibility as you can use them on both low voltage and millivolt systems. Even so, units designed for millivolt systems can’t be installed on boilers, heat pumps, or baseboard heaters.
The controls you’ll have at your disposal depend on the model, so programming the furnace or monitoring the current temperature may not be possible on all millivolt thermostats. Read our guide to water heater systems if you’re unsure which water heater type is the best choice for your home.
How does a millivolt thermostat function?
To understand how a millivolt thermostat works, you must be familiar with the components of millivolt systems.
To start a furnace, you need to make sure that a pilot light (a small gas flame) is lit, and you must go through the manufacturer’s instructions if you’re unsure how to light the pilot light on your furnace.
Once ignited, the pilot light supplies thermal energy to the thermopile that converts it into electric energy. A thermopile consists of many thermocouples that generate a voltage that corresponds to the temperature of the pilot light.
As a result, you don’t have to connect the millivolt thermostat to your home’s electrical system because it uses thermal energy as a power source. Thermostats that utilize electronic ignition are more energy-efficient as they enable you to light the furnace’s main burner without using the pilot light.
Compatibility with other heating systems
Millivolt thermostats can be installed on all furnaces that don’t utilize electricity as a power source, but you still have to check if a particular model is compatible with the furnace you have. You won’t run into compatibility issues in most cases as long as you use these thermostats on millivolt systems.
You cannot install a millivolt thermostat on low voltage or line voltage systems because their voltage is usually 750mV or 0.75V. What’s more, the unit’s thermopile generates a direct current, and the majority of modern heating systems run on alternating currents.
Even so, some thermostats designed for low voltage and line voltage systems can be installed on furnaces that don’t run on electricity. Before installing such a device on a millivolt system, you must first check if it is necessary to modify the device.
Read our guide to cooling systems if you’re searching for an efficient way to control the temperature in your home during hot summer days.
The most important aspects to consider while choosing a millivolt thermostat
The limited temperature control options and high fuel consumption have made the millivolt heating systems unpopular. In addition, only a handful of brands is still producing the furnaces and water heaters that require millivolt thermostats.
Consequently, finding a thermostat compatible with your furnace can be difficult because you have limited options at your disposal. In addition, smart or programmable thermostats are usually incompatible with millivolt systems unless the unit is modified to fit this type of heating system.
We’ve shortlisted some of the most important factors you need to consider while searching for a millivolt thermostat, so let’s take a closer look at them.
The furnace type and model
Most millivolt heating systems come with a matching thermostat that lets you regulate the temperature. If the unit’s original thermostat breaks down, the best course of action is to look for the same model.
Even though these thermostats can be used with different millivolt systems, they’re not compatible with all furnaces powered by electricity. That’s why you must find out the thermostat model and the furnace and check if they’re compatible.
Also, you need to make sure that the unit’s voltage is suitable for the furnace on which you want to install it.
Design and features
The level of control a thermostat can offer varies from basic temperature adjustments to automatic temperature changes during different parts of the day.
The vast majority of thermostats designed exclusively for millivolt systems aren’t programmable, and you must opt for a universal unit if you want to program your fireplace gas furnace or tankless water heater.
The basic models don’t feature displays, making it difficult to increase or decrease the temperature for just a few degrees. More advanced units have displays of varying sizes, and the information they show usually includes the current room temperature, time and date, or the mode of operation.
Remote and voice control options
All classic millivolt thermostats are manual, and controlling them remotely is impossible. However, recent models that are compatible with several types of heating systems offer multiple remote control options.
Wi-Fi-enabled units let you adjust the furnace’s output from a smart device, while some models can be paired with virtual assistants and controlled by voice. First, however, you must learn more about the availability of these features on millivolt systems, even if the thermostat you chose is Wi-Fi-enabled.
Geofencing features
Several manufacturers of smart thermostats produce models equipped with the geofencing option that switches the furnace on every time you enter your home.
The thermostat must have Wi-Fi access for the feature to work, and you must have an app on your phone that lets you toggle the feature off and on.
Even though these thermostats can be compatible with some millivolt systems, you must make sure that a particular model can be installed on your furnace.
Cost and warranty
These temperature-controlling devices are very durable, and chances are that you’ll never have to replace the furnace’s original millivolt thermostat.
Aftermarket models usually come with warranties that last between 12 months and 5 years, so you won’t have to worry about covering the reparation costs if any of the unit’s components break down.
Besides, millivolt thermostats are affordable, as the most expensive models with high-end features cost less than $100.
The advantages of millivolt thermostats
Easy installation process
Due to their two-wire design, millivolt thermostats are incredibly easy to install. Connecting the device to a furnace takes only a few moments as you just have to fasten the wires to the furnace’s screw terminal.
Multiple power sources
Besides relying on a thermopile mechanism to convert thermal energy into electricity, a millivolt thermostat can also draw power from batteries. This enables you to choose the power source best suited for the millivolt heating system you have.
Long lifespan
These devices don’t break down easily, and they remain operational for a long time. So once you install a millivolt thermostat, you’ll be able to use it for years. Besides, they are very affordable, so replacing them in case they break down isn’t going to cost you a fortune.
The disadvantages of millivolt thermostats
Largely outdated
Although not completely obsolete, the millivolt thermostats have become very rare. The vast majority of households in the United States use low voltage heating systems, and you’ll only encounter a millivolt heating system in old buildings.
Top 5 best millivolt thermostats
Honeywell CT53K1006 – The best thermostat for millivolt heating systems
Designed for 750mV heating systems, the Honeywell CT53K1006 millivolt thermostat is a perfect fit for wall furnaces and floor heaters. The two-wire design enables you to install this unit in just a few quick steps.
There are 5 preset temperature points that range from 50F to 90F, and you can switch between them effortlessly. However, you cannot program this thermostat or control it remotely, and you can only use it with heating systems.
This Honeywell model doesn’t have a display which makes it difficult to read the furnace’s current temperature accurately.
Pros
- Compatible with most millivolt heating systems
- Quick installation
- Compact design
- Affordable price
Cons
- No display
- Programming the thermostat isn’t an option
This Standard Heat and Cool Non-Programmable Thermostat is easy to install and even easier to use with its lever control and clearly marked modes.
Orbit 83521 – The most versatile millivolt thermostat
Besides millivolt heating systems, the Orbit 83521 thermostat is compatible with one-stage electric furnaces, heat pumps, central air conditioners, and other cooling and heating systems.
This unit is programmable, and you can use it to schedule the times when the furnace should start working automatically. The Orbit’s thermostat is battery-power, and it doesn’t require an auxiliary heat source to function normally.
It also features Energy Star presets that can lower the system’s power consumption by 33%. The display shows all relevant information and enables you to monitor the room temperature.
Pros
- Precise temperature adjustment
- Excellent energy-saving features
- Compatible with a broad range of heating and cooling systems
- Allows users to create 7-day schedules
Cons
- May not be compatible with all millivolt heating systems
- Not Wi-Fi enabled
Beautiful and contemporary design complements any décor, with a large display and warm backlight for easy viewing even from across the room.
Emerson White-Rogers 1F80-0224 – The best battery-powered millivolt thermostat
The Emerson White-Rogers 1F80-0224 is a simple thermostat that has unimpressive features. Despite this, it still lets you program the schedule your heating system should follow, and it offers several Energy Star presets.
This unit isn’t designed exclusively for millivolt systems, and you can use it with numerous other single-stage cooling and heating systems. However, you should check if this Emerson’s model is compatible with your furnace and how difficult it is to install it.
The thermostat can be powered through the heating system or by two AA batteries.
Pros
- Programming the unit is easy
- Simple temperature adjustments
- Displays current room temperature
- Energy-saving presets
Cons
- No remote control
- Not suitable for all millivolt systems
Blue 2" thermostats provide an easy-to-read 2-inch square backlit display with both heat pump or single-stage models available. Easy-to-see display characters provide a step up from the available 70 series.
Lux Products TX9600TS – The best programmable millivolt thermostat
You can regulate the temperature in your home with the Lux Products TX9600TS on all types of heating or cooling systems. What’s more, the thermostat is equipped with a geofencing feature that lets you control the temperature in your home even while you’re away.
The unit’s also compatible with Google Assistant and Amazon Alexa, enabling you to issue voice commands when you want to start or stop the heating and cooling systems in your home. The thermostat’s compact design makes it easy to find a suitable space for it on a wall.
Pros
- Compatible with most cooling and heating systems
- Simple installation process
- It offers several remote control options
- Features an energy consumption monitor
Cons
- Limited compatibility with millivolt systems
- Expensive
The touchscreen Lux TX9600TS thermostat gives homeowners easy access to control temperatures with the touch of a finger. The Lux TX9600TS features a large digital lighted display that makes the touch screen easy to read and program.
Braeburn BRA 1220 – The millivolt thermostat that is the easiest to use
The lack of advanced features makes the Braeburn BRA 1220 thermostat easy to use. This model has only basic functions that let you set a preferred temperature of the heating or the cooling system.
The miniature display shows only the current room temperature and the temperature you selected. In addition, this thermostat doesn’t let you program the system’s schedule or use power-saving presets.
Moreover, this 24V unit is not compatible with all types of millivolt systems, and you must check if you can use it with the furnace or the water heater in your home.
Pros
- Long warranty period
- Easy to use
- Displays current room temperature at all times
- Simple installation process
Cons
- No backup power source
- Overpriced
The Braeburn BRA 1220 thermostat is simple to install and use. The device can work with heating and cooling systems. Users can reduce or increase the temperature of their homes.
Frequently asked questions about millivolt thermostats
Question: How to know if I need a millivolt thermostat?
Answer: Checking the power source a heating system uses is the easiest way to determine if you need a millivolt thermostat since furnaces and water heaters that run on electricity aren’t compatible with these thermostats.
Question: Are millivolt thermostats installed on the furnace?
Answer: In most cases, you have to connect the millivolt to a furnace or a heater, but some models can be mounted on the wall away from the furnace.
Question: How to know which millivolt thermostat is compatible with my heating system?
Answer: You should check which thermostat the furnace’s manufacturer recommends. If you don’t have access to the manual, you should consult with a licensed technician to find out which thermostat is compatible with the millivolt system you have.
Question: Are millivolt thermostats difficult to install?
Answer: Installing a millivolt thermostat is easy, but failing to attach the wires to a heater or a furnace properly can damage the entire heating system.
Our verdict: How to choose the best millivolt thermostat
The process of finding a millivolt thermostat that is compatible with your home’s wall or floor heating system can turn out to be complicated, as only a handful of models on the market are compatible with all millivolt heating systems.
To complicate matters further, the manufacturers don’t offer information regarding the thermostat’s compatibility with different furnace or water heater models.
We recommend choosing the Honeywell CT53K1006 millivolt thermostat because it works with most versions of millivolt systems. On the other hand, a model like the Lux Products TX9600TS is only a good option if you’re certain that it is compatible with your heating system.
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Hopefully, this guide has helped you find the best millivolt thermostat for the furnace you’re using. Share your opinions with us in the comments, or continue reading our guide to the best propane conversion kits to find out how to change the type of fuel your gas furnace is using.
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