How Does the Nest Learning Thermostat Work?

How Nest Thermostat Learns Your Temperature Preferences?

Last updated: May 18, 2018

Just how does the Nest thermostat work anyway? 

Most users would have to assume that it doesn't resemble a regular thermostat internally, but it has to be able to do the job of a regular thermostat somehow.

Alphabet's engineers combined the latest smart technology with the functions of a regular traditional thermostat, which gives you the option of installing one anywhere an old rotary model happens to be hanging on your wall.

They did this by marrying two very different pieces of hardware.

A display and a main printed circuit board (PCB) do all of the computer-based magic that makes the Nest Learning Thermostat so smart.

The base holds a connection terminal and a tubular spirit level to replicate the functions of a traditional thermostat.

The way they did this is pretty interesting in its own right, and learning more about how this technology works can prove very useful if you ever want to install or repair your own smart thermostat.

What is the Nest Learning Thermostat?

Before you can tackle the issue of how does Nest thermostat work, you'll probably want to get a better grasp on what the device is first. By combining programmable electronics with a self-learning wireless module, Nest devices optimize the heating and cooling of a building to conserve energy beyond what could be done with a traditional programmable thermostat. The newer Nest 3rd Generation devices use special machine learning algorithms to monitor the temperature in a dwelling to get a good reference figure.

Eventually, this reference temperature data provides a matrix for the thermostat to learn what a person's schedule is like and how they like their home to feel. Built-in sensors and the location of smartphones allow them to know when the house is empty, which ensures they dial back how much energy the HVAC system is using.

Nest learning thermostat box content

All 3rd Generation devices support hybrid HVAC systems and they can even control a humidistat. Nest is slowly phasing in what they've termed E Generation devices, which feature many of the same features as Nest 3rd Generation thermostats but at a lower cost.

In addition to these features, the Nest 3rd Generation thermostats can handle multiple heating and cooling stages. Those who enjoy integrating their automated devices together will appreciate the fact they can control these through a mobile app as well. Nevertheless, things weren't always so easy.

The first Nest thermostat was released in 2011. It didn't feature the high-resolution display that modern units do, since this kind of technology was only added a year later. By the time the 2nd Generation devices premiered in 2012, they also featured pull and push tabs as well as ribbon cables. This brought the technology close to what one might find in a laptop or tablet computer. Here is some of the features Nest introduced over the years:

Nest thermostat features over the years

How Does Nest Thermostat Work

Like most complex electronic devices, Nest Thermostats use a number of sophisticated subsystems to get the job done. The most expansive of these has to do with the onboard learning module. It might surprise you to learn that each of these thermostats runs a full-sized operating system like any consumer digital device. Here is the video explainer how the Nest learning thermostat works:

Nest's Machine Learning Feature

Nest devices use digital signals to learn about your preferences. Computer scientists call these signals opcodes. As soon as you activate your new thermostat, it begins to learn about what you prefer even though it takes a few days to get completely acclimated. System Match technology changes the Nest's algorithms and activates a few differing features depending on the HVAC unit you have. It also reads what kinds of voltages are moving through the wires hooked up to it in order to find out more about how your furnace and air conditioner are wired.

Seven Days of Learning

Once it detects the type of equipment you're using, the device goes through a seven day learning period to find out more about what temperature your home should be kept at.

First Day

If you change the temperature at all on the first day, the Nest unit holds it until someone changes it manually again. Nest Leaf icons will appear whenever you have selected a temperature that the unit considers energy efficient. It then makes a record of these settings to add to the learning matrix and stores them in a special memory location.

Second Day

The thermostat starts to keep a personalized schedule using temperatures set on the first day. It also begins to track whether or not people walk in front of the device. Nest units keep this information in a separate file in non-volatile memory. Due to the way file modification dates work, it starts all days at midnight. Adjustments made late at night don't influence the early morning as a result.

Third through Fifth Days

Once Nest has a record of a basic schedule, it begins to transmit the data to the Nest app if you've connected it to a network. Otherwise, you can view information that it has collected on the display screen. It will continue to change this basic schedule while keeping a list of timestamps and temperatures on file so it can constantly compare what it learned before.

Sixth and Seventh Days

While the Nest unit doesn't stop learning, it doesn't keep recording every small change after the sixth day. On day seven, the thermostat only records patterns of at least two similar changes. These changes could include turning it to the same temperature two consecutive days at about the same time or making the same changes on the same day in consecutive weeks.

Growing Trees with Your Thermostat

While the Nest thermostat might be designed to save energy, there's another way it can help to grow trees. It takes all the temperature data that it collects over this time period and sorts it into special tables. Some of these tables are organized with a branching tree structure to help it find information faster while others are organized in straight tables in the same way a human might organize information into a table.

Nest learning thermostat schedule table

Each time it learns a bit of new information about the user, it writes a file onto a root system that's based on the same structure used by Linux PCs. In fact, each Nest Learning Thermostat is running an extremely specialized miniature distribution of the GNU/Linux operating system. The Linux kernel allows it to communicate with these files while some basic Unix-like tools, including the GNU packages and BusyBox, support a software stack Nest Labs wrote in the C programming language.

To put this into perspective, think of how the device you're reading this on handles files. You've probably saved something before and seen that the file itself reads the date and time you saved it at. This information about the saved information, which is called metadata, is what the Nest Learning Thermostat system uses to learn more about your behaviors. While it superficially sounds rather technical, the whole concept is simple if you just think about how you use your own devices on a daily basis.

Collecting Sensor Data

You could say that these thermostats have a sixth sense. Each Nest unit uses built-in motion sensors to track the motion of people in the home. Thermal sensors work like miniature thermometers to accurately track the indoor temperature. Depending on how your unit is configured, it might also look for a wireless signal to track weather data over a network.

If it notices that people are out of the house, then it will dial back the furnace or AC to save power. More efficient heating and cooling schedules can be set as soon as it knows there's a major shift in temperatures coming. For instance, if it knows it will be warmer during the afternoon, Nest thermostats will dial back the furnace for that specific time while making sure to restore heat soon enough to prevent power getting wasted from having to heat the house back up again if it gets too cold.

Other Ways that Nest Technology Saves Energy

Depending on how you use your furnace or air conditioning, you could slash your power usage by up to 10 percent. They also save power through social engineering. Those Nest Leaf icons notifying users of when their settings conserve power are an excellent way of ensuring that homeowners don't go too far out of expected boundaries. Here is the video from Nest where you can learn about its features, which saves energy:

Some people have even reported feeling a bit guilty if their Nest unit reminds them that they're wasting power! On top of this, the fact that they can be controlled remotely means that homeowners can turn off the furnace from work if they find out they forgot to before leaving that morning.

In a nutshell, Nest thermostats consist of a digital module attached to a traditional thermostat back. By using digital code, they're able to make a constant file record of minute changes made by a homeowner to their surroundings. Algorithms then calculate the best possible HVAC settings based on this record. Since these settings are often more efficient than those set manually by an end user, they can ultimately reduce energy consumption.

Further Reading

For further reading please refer to the following sources:

How Does the Nest Learning Thermostat Work