What is Multistage Heating and Cooling? How to identify if you have one?

You might want to know about the compatibility of your system with the smart thermostat. This is quite simple, just look at whether your 24v HVAC system is a multistage or single stage. Now, you might be wondering how could you tell if you own a 24v HVAC system or not?

Don’t worry, I’ve provided a distinction between single-stage and multistage systems so that you’ll not be confused.

  • Single-stage systems could be perfectly represented as “on-off”

The single-stage system is either entirely off or blowing cold (or hot) air at ample strength. They are the older version of the HVAC models. The brand-new models are seen in small houses or/and in more tropical climates.

  • Multistage systems come with level, normally two, “high” and “low”

Usually, multistage systems are built for two levels, is “high” and “low”. However, the system with 3 stages, will comprise of “high”, “low” and another additional stage “medium”. You can understand this with the example of a ceiling fan or a hairdryer. As they offer different levels to their users, the multistage systems are just like that.

Unlike the single-stages system, multistage systems are prevalent in more modern and larger residences. These systems are often seen in places with very hot or very cold climates.

In comparison to a single-stage system, multistage systems are more energy-saving. Operating at full force might make your home get cold/hot quicker. However, you can normally gain more energy savings just by getting your liked temperature steadily. Your smart thermostats are built in a way to perform this operation for you. You don’t have to manage between the stages which are in use.

As you look at different smart thermostats, there’s a designation provided to them such as “2C/2H”. You might have noticed these designations, now what do they indicate? This simply means that the smart thermostat provides up to 2 degrees of cooling (2C) and 2 degrees of heating (2H). It is alright if you only have 1 degree of cooling or heating.

How Can You Determine If your multistage HVAC system is heating or cooling?

The best method to tell if you have a multistage cooling/heating or not is to simply remove the base off of your current smart thermostat and check the wires setting within it. You would have to look at the wires to determine if your thermostat is compatible enough to connect with your HVAC device. So, it is better to become familiar with your thermostat.

After you’ve removed the base of your smart thermostat, take a glance at the wiring which leads to the terminals, especially the Y, Y1, W, and W1 terminals.

However, this is only applicable to the system with 24V. Now, let’s understand how you can identify between a single-stage system and a multistage system.

Nest Thermostat

Related ArticleWhat is Geofencing and how smart thermostat use it?

Classifying The Single-stage System

  • The standard single-stage system has only one wirework for cooling (either the Y1 or Y connector) and one wirework for heating (either the W1 or W connector).
  • The heat pumps of a single-stage system will have only one wire that will lead into the terminal Y1 for both cooling and heating.

Classifying The Multistage System

Unlike single-stage systems, multistage systems consist of multiple cooling wires and/or heating wires. Normally, the heating cables are inserted into the “W” terminal. Whereas the cooling cables are inserted into the “Y” terminals.

  • Standard 2-stage heating has wires which lead to the terminal W1 and W2.
  • Standard 3-stage heating has wires which lead to the terminal W1, W2, along with W3.
  • Standard 2-stage cooling has wires which lead to the terminal Y1 and Y2.

Originally, Some of the HVAC systems depended on the heat pump till the external temperature became too chilled for the pump to maintain on its own. They have a wire and an AUX heat which leads to either the AUX terminus or the W2.

What Do Two Sets Of Marks Indicate In A Smart Thermostat?

Sometimes it happens that a smart thermostat has two sets of marks for the terminals. Here, one of the sets is for a system called “conventional” and the second set is utilized for the heat pump.

Honeywell thermostat

When There Is A Short Wire Connecting E and W2

You can understand this with an instance, the heat pump is usually backed up by an “emergency” heat if it more-or-less breaks. There’s a chance that you have a setting like this in your heat pump.

As it is 2-stage heating, the wiring setup might get mixed. For example, the wire within terminal “E” can go inside terminal W2. If you have a Nest thermostat, then the * (star) terminal. Most probably the thermostat will require whether it’s emergency heating while setting or not.

Which Thermostat Is Competent For The Multistage Cooling and Heating System?

Well, the answer is all of them. Almost every smart thermostat available on the market nowadays is competent enough to support the 2 degrees of cooling and 2 degrees of heating.

However, you should be aware of some of the distinctions between them. The 3rd generation of Nest Learning Thermostat in the market is exclusively the only model of a smart thermostat to support the 3 degrees of heating. The rest of the smart thermostat models can only support the 2 stages.

The E generation of Nest thermostat supports only 1 degree of cooling and 1 degree of heating. Apart from that, you also get an additional stage that consists of either cooling or heating. To make it simpler, you can either have 1H/2C or 2H/1C, but you cannot have 2H/2C with Nest E.

You should have a look at the amount stages that are supported by various kinds of HVAC systems. If your HVAC system includes a heat pump, then there are several smart thermostats that can support added stages.


Standard Forced-air Setups

Product  Heating  Cooling
Ecobee4 2H 2C
Ecobee3 Lite 2H 2C
Nest Learning Thermostat 3rd Generation 3H 2C
Nest Thermostat E 2H/1C 2C/1H
Honeywell Lyric T5 2H 2C
Emerson Sensi 2H 2C
Lux Geo 2H 2C
Honeywell Wi-Fi Smart Thermostat 2H 2C

Heat Pump Setup

Product  Heating Cooling
Ecobee4 4H 2C
Ecobee3 Lite 2H 2C
Nest Learning Thermostat 3rd Generation 2H 2C
Nest Thermostat E 1H*
Honeywell Lyric T5 3H 2C
Emerson Sensi 2H 2C
Lux Geo 2H 1C
Honeywell Wi-Fi Smart Thermostat 2H 1C

As mentioned before, the E generation Nest Thermostat only supports the heat pump of single-stage with or without the AUX heat. Along with that a separate heat pump for a single-stage dual fuel. Virtually, it is not competent for any other type of heat pump, for example, a 2-degree heat pump with or without AUX heat or a 1-degree heat pump with distinct 2-degree dual fuel.

Also ReadNest Thermostat showing low battery even after charge? 

Wrapping it up

Some of the most prevalent smart thermostats are available in the market as mentioned above. With that, I hope that this read helped you with learning the distinction between multistage and single-stage cooling and heating. Along with that, I hope it helped you to pick up the smart thermostat of your choice!


I spend each darn end of the week taking a shot at home tasks and trimming down the “nectar do” list. This is where I share the majority of the undertakings I’ve done and things I’m learning.

Recent Posts