Understanding Low Voltage vs. High Voltage Thermostats

This guide explains the difference between low voltage and high voltage thermostats and helps you determine which Mysa product is the right fit for your home.

What Is a Low Voltage Thermostat?

A low voltage thermostat operates at 24V and is used to control central heating and cooling systems. Instead of powering the heater directly, it sends a signal to your HVAC equipment telling it when to turn on or off.

Low voltage thermostats are typically found in homes with:

• Forced-air furnaces

• Central air conditioning systems

• Heat pumps

• Boilers (hydronic heating)

• PTAC units

• Fan-coil units

If your home has a furnace with ductwork, a central AC unit, or a heat pump, you almost certainly have a low voltage system.

What Is a High Voltage Thermostat?

A high voltage thermostat operates at 120V or 240V and directly controls the flow of electricity to your heater. The thermostat is wired in-line between your electrical panel and your heater, acting as an on/off switch for the power supply.

High voltage thermostats are typically found in homes with:

• Electric baseboard heaters

• Convectors

• Fan-forced wall heaters

• Radiant ceiling or wall heaters

• Electric in-floor heating mats and cables

These systems are common in apartments, condos, and older homes — especially in Canada and the northeastern United States.

How to Tell Which Type You Have

The easiest way to determine your thermostat type is to look at your existing thermostat and heating system.

Signs you have a low voltage (24V) system:

• Your home has a furnace, heat pump, or central AC unit

• Ductwork or vents are visible throughout your home

• Your thermostat has thin, multi-colored wires (red, white, green, yellow, blue) behind the faceplate

• The thermostat wires connect to labeled terminals such as R, W, Y, G, and C

Signs you have a high voltage (120V/240V) system:

• Your home has baseboard heaters, convectors, or wall-mounted electric heaters

• Each room has its own thermostat controlling one or more heaters

• Your thermostat has thick wires (typically 12 or 14 gauge) behind the faceplate

• The thermostat connects directly to your electrical panel via a dedicated circuit breaker

Warning Warning: Never open your thermostat faceplate without first turning off the circuit breaker that powers it. High voltage wiring at 120V or 240V can cause serious injury.

Which Mysa Product Do I Need?

Mysa makes smart thermostats and controllers for different heating systems. Match your home to low voltage (24V) or high voltage (120V / 240V) first, then choose the product line below.

Mysa Smart Thermostat (low voltage — 24V)

The Mysa Smart Thermostat replaces a standard wall thermostat on central HVAC. It uses 24V control wiring (terminals such as R, W, Y, G, and C) and does not power electric resistance heaters directly.

Choose this if you have:

• Forced-air furnace, heat pump, or central AC

• Thin, multi-colored thermostat wires to labeled terminals

• Ductwork or a central air handler (not one thermostat per baseboard zone)

See Mysa Smart Thermostat Overview and the compatibility guide before you buy.

Mysa for Electric Baseboard Heaters — V2 and LITE (high voltage — 120V / 240V)

Mysa for Electric Baseboard Heaters V2 and Mysa LITE for Electric Baseboard Heaters are line-voltage thermostats. They switch 120V or 240V power to electric baseboards, convectors, and fan-forced wall heaters — one Mysa per heater zone.

Choose this if you have:

• Electric baseboard, convector, or fan-forced heaters

• Thick supply wires (often 12 or 14 gauge) and a dedicated breaker per thermostat

• A wall thermostat in each heated room (or zone), not a single central HVAC stat

Compare models: Mysa for Baseboards: V2 vs Lite Comparison. Check heater fit: Is Mysa for Baseboards Compatible With My Heating System?

Mysa for Electric In-Floor Heating (high voltage — 120V / 240V)

Mysa for Electric In-Floor Heating is a line-voltage thermostat for electric radiant floor mats and cables. Like baseboard Mysa products, it controls 120V or 240V power to the heating load and may use a floor sensor.

Choose this if you have:

• Electric in-floor heat (not hydronic tubes in concrete)

• High-voltage wiring at the thermostat location

Start with Mysa for In-Floor Heating: Product Overview and the In-Floor Heating Compatibility Guide.

Mysa for Ductless Mini-Split Heat Pumps

Mini-split systems are usually controlled by a handheld remote, not a wall thermostat on your heater circuit. Mysa for Ductless Mini-Split Heat Pumps is an IR controller that pairs with your indoor unit — it is not a 24V central stat or a 120V/240V line-voltage replacement.

See Mysa for Mini-Splits Overview and mini-split compatibility.

Hot water baseboard with a low-voltage wall thermostat

If you have hydronic (hot water) baseboard or radiant heat and a 24V wall thermostat that opens zone valves or boiler relays, you may still use the Mysa Smart Thermostat — not the line-voltage baseboard or in-floor products. See Installing Mysa Smart Thermostat with Hot Water Baseboard Heating and Zone Valves.

Quick reference

Related guides

• Mysa Compatibility Checker

• Mysa Smart Thermostat Compatibility Guide

• Mysa for Baseboards Overview

• Mysa for In-Floor Heating: Product Overview

• Mysa for Mini-Splits Overview

Still not sure?

Use the Mysa Compatibility Checker or contact Mysa Support with a photo of your existing thermostat wiring (breaker off, faceplate removed).