How the Nest Learning Thermostat Works

Can a small, simple device really change the way you live and teach you to conserve energy?
Can a small, simple device really change the way you live and teach you to conserve energy?
Image courtesy of Nest Labs

Brrrrrrr. How did it get so cold in here? Did someone mess with the thermostat? The household temperature setting has long been the source of arguments between cohabitators, but you probably don't think much about your thermostat until you're uncomfortable.

Your heating, air conditioning and the ductwork that carries and recycles air between rooms make up the HVAC (heating, ventilation and air conditioning) system for your home. Data from the U.S. Department of Energy suggests that your HVAC system accounts for about half of the energy consumption in your home [source: DOE]. For those with electric heating and air conditioning, that's half your home's electric bill, too.

You control your home's HVAC through your thermostat. All you have to do is select your heating and cooling options and to set your desired indoor temperature. The thermostat does the rest, switching systems on and off based on the temperature it detects in the room.

The Nest Learning Thermostat goes beyond this simple temperature detection to make a real impact in your HVAC energy consumption. In this article, we'll see what Nest can do, how it does what it does, who's behind it and what challenges it faces in the HVAC industry.

To understand Nest's value, let's first look at what other thermostats do. All thermostats let you set a desired temperature and monitor the current temperature. You can also switch between heat and AC.

Many thermostats rely entirely on you to set the temperature. Though in recent years, manufacturers have offered programmable thermostats that can help you save on energy. This lets you program certain temperatures for certain times of the day -- letting you automatically lower the temperature when you'll be out of the house, for example. However, due to the complexity of these thermostats, people don't always program them correctly, which can negate most, if not all, of their energy-saving potential.

The Nest Learning Thermostat aims to solve this problem. Nest actually programs itself by learning your behavior patterns and desired temperatures for certain days and times during the week, and then building a schedule for your HVAC. It's not the only smart thermostat on the market, but Google's purchase of Nest Labs for a reported $3.2 billion in January 2014 has made it the most famous.

So who's the brains behind Nest? Would you believe it's the same mind behind the iPod and iPhone? Before we get into the technical details, let's look at how Nest got its start.

How the Father of the iPod Got Into Thermostats

Nest creators Matt Rogers (left) and Tony Fadell (right)
Nest creators Matt Rogers (left) and Tony Fadell (right)
Image courtesy of Nest Labs

Prior to 2008, Tony Fadell was a legend at Apple. Fadell is the father of the iPod, having led the Apple team that developed the first 18 generations of the iPod and the first three generations of the iPhone.

After he retired in 2008, Fadell, who owns more than 100 patents, concentrated on building his new house in Lake Tahoe. It was during that time that he had an innovative idea to improve the thermostat. He took that vision to his former colleague Matt Rogers, who was responsible for iPod software development. Seeing value in the idea, Rogers joined Fadell in nurturing it to fruition [source: SmartPlanet].

There was only one problem: Fadell and Rogers knew nothing about the HVAC industry.

So, the duo sought advice from HVAC professionals from varying climates across the U.S. These professionals were skeptical about the idea, but curious enough to lend a hand. The information these experts provided helped Fadell and Rogers gain a deeper understanding of how and why people used their thermostats [sources: SmartPlanet, Fadell].

Armed with information and ideas, Fadell and Rogers redesigned the thermostat from scratch. The result was the Nest Learning Thermostat, the central product from their new company, Nest Labs. Their thermostat includes features that reflect their Apple roots, such as a sleek interface and multi-device connectivity.

Next, let's check out the features that have made a thermostat such a media and consumer darling.

Nest Features: Improved Design

The Nest Learning Thermostat has both energy-saving technology and an innovative design. Before we look at the energy-saving features, check out these design highlights that make Nest a cool gadget to show off to your friends:

  • Nest works with many existing HVAC systems, making it relatively easy to install in place of an existing thermostat.
  • The circular interface fades to a black screen saver when not in use.
  • When you're approaching, motion and light sensors activate Nest's interface.
  • Nest's circular outer ring is the dial you turn to adjust the temperature.
  • Nest's body is a reflective silver-gray -- originally brushed aluminum and plastic, but now stainless steel.
  • Nest uses a color background on the screen to indicate whether you're cooling (blue) or warming (orange) your home.

The second generation of the Nest, which came out in October 2012, is around 20 percent slimmer than the original. The assembled unit, including device and base, measures 3.27 inches (83 millimeters) in diameter and 1.26 inches (32 millimeters) in height.

Although the overall shape and usability remain largely the same, the new model has some other design improvements. The grill that housed the sensors has been replaced with a smooth, opaque black plastic surface that blends more seamlessly with the device. The entire outer ring is now a single rotating piece, whereas before you turned a separate front portion of the ring. And the internal connectors have been arranged in a circular pattern to allow room for two more connection points.

Nest Features: Saving Energy

The Nest display tells you how long it will take for your home to reach the desired temperature.
The Nest display tells you how long it will take for your home to reach the desired temperature.
Image courtesy of Nest Labs

The following Nest features are designed to appeal to consumers interested in saving energy:

  • Nest uses various inputs to observe your day-to-day routine and uses them to maintain your HVAC schedule automatically, based on what it learns. (The company calls this Nest Sense technology. We'll cover it in more detail later.)
  • Nest creates an auto-away mode based on what it's learned. This sets a temperature for minimal HVAC activity when you're not in the building. You can also set an away mode manually if you wish.
  • While it's actively heating or cooling, Nest displays an estimated time for the system to reach the desired temperature.
  • Nest displays a green leaf any time the thermostat is running at energy-saving settings. This can help teach you to make energy-saving decisions. For example, if Nest has learned that you typically run your AC until the house is 74 degrees Fahrenheit (23.3 Celsius), you could turn up the temperature until you see the green leaf to save energy. The leaf will always appear at cooling settings of 84 degrees Fahrenheit (28.9 Celsius) or higher and heating settings of 62 degrees Fahrenheit (16.7 Celsius) or lower, but its threshold will change based on your habits.
  • Nest lets you know what activity (between auto-away, your own adjustments and the weather) resulted in the greatest energy savings throughout the day.
  • Nest uses WiFi to connect to your account at nest.com. This feature allows you to monitor and adjust the Nest remotely from the Web site.
  • Nest supports a mobile app available for Apple iOS devices (iPod Touch, iPhone and iPad) and Android devices. The app turns your mobile device into a remote control for your Nest.
  • You can add Nest to any number of thermostats in a multi-thermostat building. They will work alongside other thermostats, but note that each of Nest's energy-saving features only applies to the rooms in its sensor range and to the HVAC components it controls.
  • A Nest account can manage up to 10 Nest devices, whether they're in the same building or at multiple locations.

As we've noted, Nest offers tech-savvy users options for manually programming the thermostat. However, Nest was developed for users who'd rather just turn the dial when necessary. For that probable majority, Nest's VP of Technology, Yoky Matsuoka, offers these tips for teaching your Nest to save energy.

Next, let's take a closer look at the Nest Sense technology.

Nest Technology: Nest Sense

We know the main features of the Nest Learning Thermostat. But what's behind that sleek black screen? The core technology behind Nest is a combination of its sensors, hardware and algorithms. The company calls this Nest Sense. Let's take a look at how Nest Sense works.

Part of Nest Sense's job is to gather data to use in its calculations. This data goes beyond just measuring the temperature in the room. In fact, Nest gathers data from the following sources:

  • Three temperature sensors, designed to get a more precise measurement than a single sensor
  • A humidity sensor to gauge the moisture in your home's air
  • Motion and light sensors that detect activity in the room at a 150-degree angle
  • A WiFi connection to get weather data about your area from the Internet

Using data from these sources, Nest Sense creates a schedule for your HVAC. The schedule includes the following:

  • Device settings to activate at specific times of the day on each day of the week
  • Auto-away times, which are intervals that Nest has determined you're not at home

You can view this schedule from the Nest thermostat's interface or from your Nest account online. If you want to make manual schedule changes, you can do that, too. Manual adjustments can be useful when you'll be away from home for several days, or if you'll be at home instead of away during a typical work or school day.

Software updates and bug fixes are rolled out regularly, and many of the updates bring new capabilities to the device. As of the 3.0 version of its software, which was released in conjunction with the second generation Nest thermostat, the device uses different algorithms depending upon what sort of HVAC setup you have, providing features that work more efficiently with that particular system. It also became multilingual, allowing control from the Nest device, the website and the mobile apps in English, French or Spanish.

Version 3.5 added the ability to control just the fan, to kick on the AC when humidity hits a certain level, and to adjust temperature settings when the device is in direct sunlight.

But what is installation and setup like? We'll examine those next.

Nest Installation

The moment you begin using your Nest, it begins observing your schedule and preferences to create a temperature schedule for your home.
The moment you begin using your Nest, it begins observing your schedule and preferences to create a temperature schedule for your home.
Image courtesy of Nest Labs

Nest's installation requirement list isn't terribly long. First, you'll need a WiFi network in the building, and that should include Internet access. With that in place, you can turn your attention to your existing thermostat.

Nest is designed to use the wires common to HVAC systems in homes and businesses today. Installation instructions start before you purchase a Nest:

  1. Visit the Nest support Web site and launch the compatibility check wizard. At the time of writing, you could use this link. Another option is to visit Nest.com, click on "Support" and scroll down to find the Compatibility Check box and link.
  2. Remove your thermostat from its mounting frame, revealing its wires. If you need help with this, click the video link in the compatibility check wizard for hints.
  3. In the wizard, check off the abbreviations matching the ports behind your thermostat where wires are connected. Even if the wizard shows a message indicating what you have before you finish, keeping checking until all your wires are accounted for. Also, don't check off any abbreviations that don't have a wire.
  4. Click "Continue" to see if your thermostat's current wiring is compatible with Nest.

If Nest's site says your system isn't compatible, ask an HVAC professional about your options. You might want to check here to find a Nest-certified Professional in your area. If you can't find one, be ready to tell your HVAC pro what you've learned and point him or her to the Nest Labs support site. Nest.com lists its supported wiring combinations here.

The second generation Nest thermostat has 10 wire connection points as opposed to original Nest's eight, so if your system wasn't compatible when the device first came out, you might want to check again. The company states that the new Nest Learning Thermostat is compatible with 95 percent of 24 volt (low-voltage) HVAC systems, up from the first generation device's 75 percent compatibility.

Once you know your home's wiring is compatible, you can purchase and install your Nest. If you're comfortable installing a light fixture or ceiling fan in your home, you can probably follow directions from Nest and install the thermostat yourself. If twisting copper wires together makes you nervous, use the Nest Certified Professionals lookup to find a professional installer in your area.

When you've installed the physical device, step through Nest's instructions to set up the software. This includes connecting to your WiFi network and your Nest account. After that, you can start using Nest to control your HVAC.

Within a week of making temperature adjustments as needed, Nest should have created a good approximate operating schedule for subsequent weeks. In addition, it never stops learning as it gathers data about you, your habits and your local weather over time.

Next, let's take a brief look at this product's advantages and challenges in the HVAC market.

Nest Advantages and Challenges

Despite all its features, though, Nest has some hurdles to overcome. As of early 2014, Nest costs $249 per thermostat. That's more than twice, and in some cases five times, the cost of programmable thermostats from established brands Honeywell, Filtrete and Cadet. Non-programmable thermostats are even cheaper, with some models costing less than $20. Because of this, Nest's only customers are likely to be people with moderate to high incomes or who place a high value on either its design or its energy-saving features.

Beyond the cost gap, Nest also faces a sea of consumers who know very little about how their HVAC systems work. Though marketing materials for the Nest describe functions of these systems in easy-to-understand language, it may still prove difficult to sell the product directly to the consumer. It's possible that Nest's target audience will eventually shift to HVAC professionals and building contractors instead of home and business owners.

In early 2012, Honeywell, the biggest brand in thermostats in the U.S., threw down yet another gauntlet for Nest Labs. On Feb. 6, 2012, Honeywell filed a patent infringement lawsuit against Nest Labs citing seven Honeywell patents. Two days later, Nest Labs accepted the challenge. In its statement, Nest Labs said, "Nest will vigorously defend itself against Honeywell's patent-attack strategy to stifle thoughtful competition, and we have the resources, support and conviction to do so." That case is on hold as of early 2014, but another company, Allure Energy, brought a patent infringement suit on May 14, 2013. Time will tell how these legal battles will play out.

In January 2014, Google announced that it would be acquiring Nest for $3.2 billion. Provided the purchase is approved by regulators, the move will get Google into the connected home device market and possibly provide Nest Labs with more resources with which to fight patent suits. The impending acquisition has raised some privacy concerns from people worried that it will give Google access to the data gathered by Nest Learning Thermostat's sensors, as well as data from Nest's other product, the Nest Protect smoke and carbon monoxide detector. Nest contends that the company will follow its privacy policy and the information will continue to be used only to maintain and improve Nest products and services.

Author's Note: How the Nest Learning Thermostat Works

I updated this article, and as a result, I'm very impressed with the Nest Learning Thermostat. I'll gladly try one out if my ancient HVAC system (and my wallet) can handle it. The new Nest Protect smoke and carbon monoxide alarm has piqued my interest, as well. The two devices can apparently communicate with each other so that they can react appropriately to developments in your home environment.

Innovative companies like Nest are providing some useful additions to the so-called Internet of things. Who knows what ubiquitous appliance will be next? I look forward to the day my refrigerator can text me that the milk has expired or tell me what I can make for dinner with its current contents. The Nest thermostat gets us one step closer to our wired homes of the future. -- BJ

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