What is a Line Voltage Thermostat? 5 Ways to Identify One


If you have electric heating, chances are you have a line voltage thermostat. While the question of what type of heating your home has is likely not something that keeps you up at night, it’s important to know if you’re thinking about smart thermostats.

Electric systems like baseboard heaters are usually pretty efficient, since you can control each area of your home individually. However, there are ways to increase their efficiency, the simplest one being a thermostat upgrade.

Smart thermostats let you control your heating and air conditioning more easily. Instead of constantly adjusting a dial or fiddling with a complicated programmable thermostat, you control everything on your smartphone. This way, you’re always comfortable, without sacrificing savings. 

Before evaluating smart options, it’s important to know what type of thermostat you currently have. This helps you choose a smart upgrade that’s compatible with your home. So, how do you know if your thermostat is line voltage? Let’s find out. 

room control by smart programmable thermostat for electric baseboard heaters

What is Line Voltage? 

In electrical systems, the term ‘line voltage’ refers to the amount of voltage running through an electrical socket or circuit. For line voltage systems, this is 120 volts or 240 volts of electricity. Most electrical appliances can handle 120V-240V of electricity, which is why most (pretty much all) appliances work straight out of the box. 

This is the primary benefit of having line voltage wiring in your home. There’s no need for extra hardware like a transformer. All you have to do is plug in your new microwave or video game console. No rewiring needed. Other benefits include lower-cost fixtures, easier installation, and energy savings for home lighting. 

But, it’s not just consumer electronics that run on line voltage. Electric heating thermostats also use 120V-240V of electricity. These are commonly known as high voltage thermostats or ‘line voltage thermostats’ and control electric heating systems like baseboard heaters. 

digital line voltage thermostat on wall

What is a Line Voltage Thermostat?

What does ‘line voltage thermostat’ mean? Line voltage thermostats control electric heaters such as resistance heaters, radiant heaters, and convection heaters. These usually come in the form of electric baseboard heaters (aka wall heaters), electric in-floor heating, fan forced heating, and in-ceiling radiant heat. 

Line voltage thermostats deliver electricity directly to heaters. So, they handle more power than low voltage thermostats that control central HVAC systems like a gas furnace. They work by measuring room temperature and controlling power delivery to maintain a setpoint (the temperature you set your thermostat). 

The thermostat will turn your heater on or off, depending on how close it is to your setpoint. If the temperature in a room goes below the setpoint, it will turn your heater on. Once the desired setting is reached, your heating system will be turned off. Generally, line voltage thermostats can use single or double pole wiring, depending on the thermostat's features.

single pole thermostat wiring

What is a Single Pole Line Voltage Thermostat?

In terms of wiring, a single pole thermostat is simple. It has two interchangeable wires and a singular switch that opens or closes the heating circuit. Opening the circuit cuts power flow to the heater, thus turning it off. Closing the circuit does the opposite and allows power to flow so that it can control room temperature.

Single pole thermostats are usually easier to install, since both wires are interchangeable. However, single pole thermostats don’t have an off setting and use power stealing. To keep the thermostat itself powered, the unit occasionally turns the heater on or off, which reduces efficiency and your comfort at home.  

double pole thermostat wiring

What is a Double Pole Line Voltage Thermostat?

Double pole thermostats require at least four wires for installation. While this makes installation more complicated, it has the benefit of being able to completely disconnect from your electrical panel. (Which isn’t possible with a single pole thermostat). 

Since these thermostats have an L2 (N) connection to power itself, power stealing is not needed. This means the thermostat can remain powered even when there’s no power being delivered to your heater(s). So, it has a true off setting.  

Note: Some electrical installations may require a double pole thermostat. So, it’s not recommended to replace a double pole thermostat with a single pole device unless directed by a qualified electrician.

How Do I Know if My Thermostat Has Line Voltage?

Knowing what type of thermostat you have in your home is critical if you’re looking for a smart thermostat, so you can find a compatible upgrade. If you're not sure what type of thermostat you have, there are some quick and easy ways to find out. 

Disclaimer: Electricity is dangerous. To ensure your safety, please take proper safety precautions, follow local electrical laws/regulations, and consult an electrician before doing any electrical work.

room with electric baseboard heaters

1) Consider How You Heat Your Home

There are many different home heating systems. While this is great since it gives homeowners  choice, the downside is it means there’s no one-size-fits-all solution for smart home thermostats. How you heat your home can be a good indicator of whether you have a line voltage thermostat. 

Home heating systems generally fit into one of two boxes: electric or central. Electric home heat is usually controlled by line voltage thermostats. Central heating is usually controlled by low voltage thermostats. 

If your home heating system doesn’t have any ductwork and runs on electricity, you likely have electric line voltage thermostats throughout your home. Baseboard heaters, fan-forced heaters, in-ceiling radiant heat, and electric in-floor heating are all examples of electric heating controlled by line voltage thermostats. 

However, if your home heating has ductwork, makes use of radiators, or is powered by heating fuels like water, gas, oil, wood, etc., you likely do not have line voltage thermostats. Furnace heating, forced air, ducted heat pumps, and boilers are all examples of central HVAC systems controlled by low voltage thermostats.  

home with multiple thermostat zones

2) The Number of Thermostats in Your Home

Another way to tell if you have a line voltage thermostat is based on how many thermostats are in your home. Electric heating is a zoned system, meaning each heater or room is controlled by a separate baseboard heater thermostat. Most homes with electric heating have multiple thermostats, as many as one for each room. So, if you have a thermostat in each room of your home, they’re likely line voltage. 

3) Check Your Thermostat Voltage

Another easy way to see if you have a line voltage thermostat is to check your thermostat’s voltage. There are a couple ways to do this:

  • Check your thermostat’s labeling: Look for a label on your thermostat. If it’s line voltage, there should be a label that reads “HIGH VOLTAGE” or a similar warning. It may also provide the voltage level itself, (i.e. 240V or 120V line voltage thermostat). This should be on the exterior of your thermostat or under the cover.

  • Use a voltage meter: Try using a voltage meter to measure how much voltage is going to your thermostat. A high reading indicates line voltage. Note: Make sure to take necessary safety precautions before trying this method.

Either method should help you answer ‘is my thermostat 120 or 240 V’ and if you have a line voltage thermostat. 

4) Count the Wires in Your Gang Box

A gang box is a metal box that holds the wires in your wall that connect to your thermostat. If you don’t have a gang box, it could be a sign that you don’t have a line voltage thermostat. You could also look at the number of wires coming from the gang box. 

How many wires do you need for a thermostat? If you have a line voltage thermostat, you should see a small number of wires separated into colored groups (ex. black and red or black and white) of 2, 4, or 6 wires. 

Reminder: Before inspecting your thermostat’s wiring, be sure to turn off power to your thermostat and heater from the circuit breaker. 

line voltage thermostat wiring

5) Thickness of Thermostat Wires

When looking at your thermostat’s wiring, also look at how thick the wires are in your gang box. If there are large, thick wires, your thermostat is likely line voltage. Thin multi-coloured wiring indicates low voltage.

If you’re still wondering, ‘is my thermostat low or high voltage’, check out this blog for a further comparison of line voltage vs low voltage thermostats. 

Will a Line Voltage Thermostat Work With Low Voltage?

Does Nest work with line voltage? Can you install any other low voltage thermostat to replace your old electric heat thermostat? Put simply — no. A low voltage thermostat like Nest or ecobee is not compatible to replace a line voltage thermostat for electric heat. 

Line voltage systems deliver power directly to your heating system rather than powering an intermediary furnace like a gas burner. This means it requires levels of power that low voltage thermostat wiring simply cannot handle without complex rewiring and safety concerns. 

Line Voltage Smart Thermostats

Now that you know more about your heating system, it's time to consider which thermostat is best for your home's temperature control. If you’re looking to save energy and money on your electricity bill, a smart line voltage WiFi thermostat is a great option.

reviewing smart wall heater thermostat features

Finding a Smart Line Voltage Thermostat 

If you’ve found out that you have a line voltage thermostat, it’s time to find the perfect smart upgrade for your home. When shopping for a smart thermostat, there are a few other things you should consider in addition to the points already discussed, including: 

  • Compatibility: In addition to knowing if you have a high voltage thermostat, there are other compatibility considerations. These include connectivity, max wattage, and the number of thermostat wires needed.  

  • Smart features: Compare the features of each smart thermostat’s app. The number of features and how they work can differ heavily between brands, so it’s important to make sure you’re choosing a product that has features to suit your needs.  

  • Integrations: Different smart thermostats have different levels of compatibility with third-party integrations like Google Home, Amazon Alexa, and Apple HomeKit. Make sure that the smart thermostat you choose is compatible with the system you use. 

For homes with line voltage thermostats, Mysa is a great smart upgrade since it’s a line voltage smart thermostat specifically designed for electric heating. Mysa connects directly to WiFi; has a capacity of up to 3,800 watts; requires at least 4 wires for installation; works with Google Home, Alexa, and HomeKit; and has many energy-saving smart features. 

If you need a 2 wire high voltage smart thermostat (meaning there are only 2 wires in your gang box), consider Sinope

reviewing electric bill savings from using line voltage smart thermostats

Benefits of a Smart Line Voltage Programmable Thermostat

There are many benefits of having a smart line voltage thermostat, some for example include:

  • Serious financial savings by minimizing the amount of heat you use. (Homeowners can save up to 26% on their monthly electric bill). 

  • The ability to control your heat from anywhere with WiFi connection. 

  • Convenience of programming automatic temperature changes with Scheduling or Geofencing features. 

  • Analysis of heating schedules, energy usage, and more for better optimization.

  • Being able to control your home heating with voice commands. 

Do You Have a Line Voltage Thermostat?

Hopefully, you now have a further understanding of line voltage thermostats. If you’re thinking about making a smart upgrade, run through these steps to help you find the best line voltage thermostat for your home. Then, you’re free to enjoy the convenience and savings of smart home heating control. 

If you’d like to learn more about smart home heating solutions, subscribe to Mysa’s email list

by LastSale
by LastSale