5 Best Line Voltage Smart Thermostats in 2021

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Line volt thermostats are an acquired taste for some homeowners and a necessity for others. They are the perfect option for baseboard heaters, convectors, and some fan-forced systems, although finding the right model for your home can challenge even the most seasoned consumers. In this guide, we’ve highlighted five of the best line voltage thermostats available to go along with some helpful buying tips.

Overview of Line Voltage Smart Thermostats

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Mysa Thermostat

Mysa Thermostat

  • Range: 41°F to 86°F
  • Connectivity: Wi-Fi
  • Programmable: Yes
  • Warranty: 2 years
Stelpro Z-Wave Plus KI

Stelpro Z-Wave Plus KI

  • Range: 41°F to 86°F
  • Connectivity: Z-Wave
  • Programmable: Yes
  • Warranty: 3 years
Honeywell T498B1512

Honeywell T498B1512

  • Range: 40°F to 90°F
  • Connectivity: None
  • Programmable: No
  • Warranty: 1-year
Honeywell CT410B

Honeywell CT410B

  • Range: 40°F to 85°F
  • Connectivity: None
  • Programmable: No
  • Warranty: 1-year
King ESP230-R MAX22

King ESP230-R MAX22

  • Range: 44°F to 95°F
  • Connectivity: None
  • Programmable: Yes
  • Warranty: 3-wire

Full Reviews of Line Voltage Smart Thermostats

The Best Smart Line Volt Thermostat

#1 Mysa Smart Thermostat for Electric Baseboard Heaters

Mysa Thermostat

We’ve seen a number of interesting products spring forth from Amazon’s Launchpad program since its inception, but we were surprised to come across a device like the Mysa thermostat. It has a design that sets it apart from every other system on the market and it has an outstanding range of features given the price.

The Mysa smart thermostat has a minimalistic design with no buttons, knobs, or dials to deal with. The front panel is the display, so the temperature is shown in large numbers along with two capacitive arrows to adjust the temp. It’s an interesting approach and one that only works because this thermostat connects to the Wi-Fi network in your home.

Through the Mysa mobile app, you can remotely control and check the temperature in your home. Energy reports will give you the lowdown on how much money you’re saving while geofencing and scheduling ensure the system only runs when it needs to. It’s efficient, and you’ll be thankful for features like Vacation Mode and Lockout as well.

Mysa designed this thermostat specifically for electric baseboard and fan-forced heaters, but it will also work with in-ceiling heaters. The temperature range on the unit is listed at 41°F to 86°F, and it can handle up to 3,800 watts at 240-volts. This sleek single-pole thermostat is a breeze to install and sports a 2-year warranty from Mysa.

Our Verdict

The Mysa thermostat is the best choice for connected homes as it works with Alexa, Apple Home Kit, Samsung SmartThings, Google Assistant, and IFTTT enabled devices. It’s more versatile than other smart thermostats and easy to install as long as you have 4-wires and a compatible heater. The only knock on this system comes into play with connectivity issues, something that tends to plague every connected device.

The Best Budget Line Volt Thermostat

#2 Honeywell Home CT410B Premium Line Volt Thermostat

Stelpro Z-Wave Plus KI

Thermostats come in all shapes and sizes, from large touchscreen digital panels to small but effective solutions. The CT410B from Honeywell Home falls into the latter category and is the best option if you’re looking for a budget-friendly line volt thermostat.

This line volt thermostat from Honeywell is small at only 4.5”H x 2.7”W and has a streamlined modern design.  It’s vented at the top and bottom with a large manual dial in the middle. While the company didn’t give a range, it appears to run from 40°F to 85°F. There are no other controls to speak of aside from a dedicated “off” setting when the dial is turned all the way to the left.

Honeywell kept the inside just as simple as the outside on the CT410B. It’s compatible with 120 and 240-volt systems and can handle up to 5,280 watts. This thermostat has a bi-metal temperature sensor and comes with a 4-wire non-polarized connection. While incredibly inexpensive, it still sports a standard 1-year guarantee.

Our Verdict

Not everyone needs a connected thermostat for their baseboard heater, and if you want something mechanical, modern, and simple, it’s hard to go wrong with the Honeywell CT410B. We did notice a variety of quality control issues with this model, but that’s par for the course with these budget-friendly units.

The Best Programmable Line Volt Thermostat from King

#3 KING Electric Programmable Line Voltage Thermostat

Honeywell T498B1512

From hydronic and commercial heaters to residential models, King Electric has something for everyone. They also have a wide range of heating accessories, including thermostats like the King ESP230-R MAX22. This inexpensive unit is a nice upgrade from mechanical models and allows for 7-day scheduling.

This digital thermostat may look simple with its 2-button control system, but it has some surprising features inside. Programming keys are hidden beneath the panel, which lets you set a 7-day schedule for your heater. That includes the ability to set four time periods each day, and the design keeps everything neatly tucked away.

There is a large backlit display on this thermostat, which can be turned off with a switch, just like the system itself. The color of the panel depends on the temperature in your home. The panel will glow a light blue at 65°F and turns warm red at 75°F or higher. King used a single pole design on this thermometer for an easy installation.

According to the manufacturer, the range on this thermostat is 44°F to 95°F. It’s listed with a 3-minute cycle rate and a 22AMP max rating. While we chose the 240-volt version of this thermostat, a 120-volt variant is also available.  This unit also has a battery backup and comes with a standard 1-year warranty from King.

Our Verdict

King did an excellent job with the ESP230-R MAX22, and it’s a well-made thermostat homeowners found easy to install. While most opted for the 240-volt version, both have received high marks from consumers. Customer support is solid if you do encounter an issue, and we love the fact you can set individual timer periods throughout the day.

The Best Z-Wave Thermostat for Baseboard Heaters

#4 Stelpro Z-Wave Plus KI Thermostat

Honeywell CT410B

We’ve seen an influx of smart thermostats in the low voltage class in recent years, but the selection of Z-Wave thermostats is still somewhat sparse. One of the best comes from Stelpro, and the Z-Wave Plus KI is an excellent choice for convection and baseboard heaters.

Billed as the first Z-Wave thermostat to work with line voltage in North America, this system allows you to sync up to other Z-Wave devices in your home. With the right hub, you can program it for use with scenes or make use of advanced automations for things like door or motion sensors. It offers more control than you’ll find from a simple Alexa-enabled device; just check the hub compatibility beforehand.

Stelpro designed this thermostat with a 2-wire or 4-wire connection to the heater, so it’s DIY-friendly from an installation standpoint. It’s sturdy, albeit a bit large at around 5” x 5” in diameter. A small backlit display is easy to read night or day, and like all the top models, you can dim or brighten up the display to suit your needs.

While there aren’t as many features with this model as you’ll find with thermostats that rely on Wi-Fi connectivity, there are a few energy management modes to choose from with Comfort or Economy. The thermostat range is 41°F to 86°F on the Stelpro STZW402WB+, which is average for connected thermostats in this class.

Our Verdict

Designed to work with electric baseboard and convector heaters, the Stelpro Z-Wave Plus KI provides a lot of bang for the buck. It may seem basic, but it can accomplish pull off some nifty tricks wirelessly provided you have a compatible Z-Wave controller. This thermostat comes with a 3-year guarantee from Stelpro.

A Retro Replacement for Line Volt systems

#5 Honeywell T498B1512 Electric Line Volt Thermostat

King ESP230-R MAX22

Honeywell has been manufacturing thermostats for decades, so it’s not uncommon to find their systems in older homes across the United States. In fact, you may recognize the Honeywell T498B1512 as it still has that classic style and is an excellent choice for a retro replacement.

This line volt thermostat bears a striking resemblance to the classic thermostats sold by the company over the years. The housing has a brushed gold finish while a manual dial that allows you to dial in the temperature. The range on this thermostat is 40°F to 80°F, while the sensor displays readings from around 40°F to 90°F.

Due to its mechanical nature, this thermostat doesn’t provide the most accurate measurement of the temperature indoors. It is easy to install, however, thanks to color-coded leads and 6” wires. The Honeywell T498B1512 will mount on any standard 2” x 4” outlet box or 4” x 4” junction box and measures 4.9”H x 2.7”W.

Our Verdict

The Honeywell T498B1512 is the best option if you’re trying to replace a thermostat from an older home and want to keep the vibe intact without going digital. While there are cheaper alternatives, this is the only one with the retro style. Some homeowners had trouble with the accuracy out of the box, but it’s easy to calibrate.

How to Find the Best Line Voltage Thermostat

Line volt thermostats are in a class by themselves as they are designed to work with electric baseboard and wall heaters. While there are other applications you can use these thermostats for, they are outnumbered by traditional models by a wide margin. That makes finding the best line voltage thermostat somewhat easier, although you’ll still want to keep the following areas in mind.

Check Your Wiring

Before you choose a new thermostat for your home, the first thing you need to do is make sure it’s compatible with your wiring. Electric heaters that use line voltage thermostats typically have two types of wiring with single or double pole circuits.

In order to know which one you have, you need to turn off the power, pull the plate off your thermostat and look at the wiring. If you have your owner’s manual, you can skip this step, but a single-pole system has two wires while a double pole thermostat has four.

Line Voltage vs. Low Voltage Thermostats

When looking for a line voltage thermostat, you will encounter dozens of listings for low voltage thermostats. While both can control heat, they are completely different and commonly confused with homeowners purchasing their first thermostat.

A low voltage thermostat is commonly used on central systems and requires very little power to operate. They are a wider selection of low voltage thermostats, but they aren’t designed to work with resistance-based or radiant heat sources. They are relatively easy to identify as well because they have thinner wires.

By comparison, any line voltage thermostat has thicker wires as it needs to carry more power to the heater. You don’t use these to control central systems, and while more expensive with a smaller section overall, they are the best option for baseboard heaters and convectors.

Single Pole Thermostat

Easy to identify by two wires, single-pole thermostats are a cheap and effective way to control heat from a baseboard heater. The main thing to remember is there is no set “off” position with these thermostats, despite what the dial may say. When the dial is set left, your system is still on – just on the lowest setting.

If that’s 40°F, your heater will automatically come on when the temperature drops below that point as it has a constant supply of power. That means the only way to cut it completely off is to disconnect the power from the panel. In the warmer months, that can become a problem when the heater is no longer in use.

On the chance that you happen to sit something near or in front of the heater and forget to move it in the winter, you could be in for an unpleasant surprise when the heater starts up. Keep that in mind, along with travel plans, if you ever plan to leave a heater with a single-pole thermostat unattended when the seasons change.

Double Pole Thermostats

On the opposite side of the spectrum are double pole thermostats. While they have two more wires than a single-pole system, they also have a dedicated off switch. You can turn these heaters completely off in the summer or whenever they aren’t in use, and never have to worry about your system coming on unexpectedly.

A double pole thermostat will cost a bit more but completely isolates the heater from the power supply. They are also a little trickier to install if you plan to handle things yourself, although that can depend on the style of thermostat you choose. Simply put, double pole thermostats are safer from an electrical standpoint and ideal for the forgetful homeowner.

Both single and double pole thermostats can come in at 120 or 240 volts. You also need to check the maximum wattage for the new thermostat and your current heater beforehand as well to make sure it can handle the load.

Types of Thermostats

Now that you have a handle on the type of wiring your current thermostat has, it’s time to think about the new one. All modern thermostats fall into one of three basic categories with Manual, Programmable, and Smart thermostats. 

Manual Thermostats – As the name implies, you’ll need to use your fingers to adjust the temperature and settings on these thermostats. They are easy to use, simple to install, and the most affordable type of thermostat if you’re not concerned with flagship features like scheduling or connectivity.

Programmable Thermostats – When you purchase a programmable thermostat, you’re going to get a few more bells & whistles, including a display. How far the thermostat lets you set a schedule in advance varies, but they are the best option for homeowners that simply want to “set it and forget it.”

Smart Thermostats – If you live in a connected home, you’ll want to consider a smart thermostat. They can include anything from geofencing capabilities to voice control and allow you to control your system without ever leaving the couch. While they come at a premium, there are models priced competitively against high-end programmable thermostats.

Line Volt Thermostat Features

There was a time when the features you had to think about on thermostats were the controls and range. That has changed significantly over the past decade, and now there are a variety of features you’ll want to be aware of before you purchase a new line voltage thermostat.

Temperature Range - Every thermostat, regardless of the style, has a set temperature range that it operates under. With heating thermostats, this tells you how cold it can get before the heater kicks on and just how toasty you can make a room. In most cases, you can expect a range between 40°F to 85°F with this type of thermostat.

Controls – The first thing you should consider on a line volt thermostat are the controls. Manual thermostats come with a dial and a few switches depending on the model, while electronic thermostats have digital controls and a small display. There are also systems that allow you to connect through Wi-Fi and other wireless protocols as well.

Display – If you purchase a thermostat with a display, check to make sure it’s dimmable. Nothing is worse than being blinded by a bright display in the middle of the night, although it should be bright enough to read as well. Touchscreen displays are an option if you’re willing to pay a premium, but rare with this class of thermostat.

Scheduling – This is a feature you’ll only find on a programmable thermostat with electronic controls, but one well worth paying extra for. The best models have 7-day programming and can offer up multiple settings each day, whereas a 5-2 thermostat allows for a set 5-day program for the work week with 2 programming days for the weekend. 

Modes – This is something that you'll find on plenty of window AC units and tower fans, but systems with a high-end line volt thermostat can take advantage of modes as well. Economy or Eco modes are a popular option, along with Vacation mode or Lockout, which keeps someone from accidentally or intentionally changing your settings.

Smart Line Voltage Thermostats

Comparing a “smart” line voltage thermostat to the best programmable models is light comparing apples and oranges. These thermostats come with a wealth of features, including the ability to use geofencing or control your unit from anywhere. This is more than one type of wireless protocol to consider, however.

Wi-Fi is the most common wireless technology used with smart line volt thermostats, and there’s a good chance you already have it in your home. If a smart thermostat is Wi-Fi compatible, you will be able to control it with a mobile app once it’s synced to your home network. Some Wi-Fi thermostats will require a hub like Alexa or Google Assistant to take full advantage of its features.

The other type of connectivity found on line voltage thermostats is Z-Wave. Thermostats that use this protocol can have a similar set of features, but Z-Wave operated on a lower frequency than Wi-Fi. The advantage of using a lower frequency means less congestion or interference from other wireless devices.

Line Voltage Thermostat Installation

Installing a new thermostat may seem like a frightening proposition to most homeowners, but many of the best line voltage thermostats are designed to be DIY-friendly. That means in most cases, you’ll only have 2 or 4 wires to deal with, although you may still need to call in a pro depending on your existing thermostat and heating system.

To install a line voltage thermostat, you’ll first want to turn off the power to the thermostat at the breaker box. Then you need to remove the old thermostat and unhook the wiring. Unless you are replacing your current thermostat with an identical replacement, you’ll need to remove the wall plate as well.

Once the old thermostat is unhooked, it’s time to install the new wall plate and get your heater back in action. When the new plate is firmly attached, you can proceed to hook the wiring back up and attach the face. The video below shows the process behind a double pole thermostat being installed.

Keep in mind, these are just basic instructions to let you know what to expect, so you should always follow the installation instructions provided by the manufacturer of your thermostat. When in doubt, don’t hesitate to call in a qualified professional to install your new thermostat. If you want to dig deeper into thermostat wiring procedures, check out our In-depth Thermostat Wiring Guide.

Warranty

If you intend to buy a mechanical thermostat or budget-friendly replacement, you shouldn’t expect much when it comes to the warranty. Most companies provide a simple 1-year guarantee on these systems, although we’ve seen premium models with similar warranties as well.

With smart or connected thermostats, you can expect the warranty to range between 2-3 years. Given the affordable nature of these devices in general, extended warranties usually aren’t recommended unless you’re buying a high-tech unit for your home.

Conclusion

Line voltage thermostats may not be as popular as their low voltage counterparts, but they are an excellent option for the types of systems we outlined in our guide. If you are interested in a traditional or smart thermostat for a central HVAC system, we have you covered

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