Anatomy Lesson: Getting to Know Smart Thermostats
Several efficiency pieces to your home start at the thermostat.
November 04, 2010 by Julie Jacobson

Remember when a “smart” thermostat was one that you programmed for each day of the week? If you’re like most Americans, you never got around to setting those daily start-and-stop temperatures. Fortunately, thermostats are smarter today, imparting useful information to homeowners, reacting automatically to cues from the utility, and enabling the remote monitoring and management of your heating, ventilation and air conditioning (HVAC) system for the utmost in energy savings and comfort.

Click here to view seven thermostat options. Here’s an in-depth look at what you need to know about today’s intelligent thermostats:

Remote Monitoring & Control
- Standalone web-enabled thermostats generally connect directly to a home’s wireless or wired network to establish two-way communications from a remote location or in-home web browser.

- Some units will send email or text alerts based on specific events such as maintenance issues (your HVAC system is working improperly or it’s time to change the filter) and high/low temperatures.

- If the thermostat has a built-in web server or connects to a web-enabled home automation system, often there is no monthly fee to use the remote-access feature; however, you may be charged monthly fees if the system utilizes an external server hosted by a third party.

- Some smart thermostats have extra communications capabilities built in, allowing the HVAC unit to respond to one or two triggers such as the press of a button on a remote control. For example, hitting button “A” on the remote control might set the temperature back a few degrees for a cool bedtime environment. For the greatest functionality, however, it’s best to connect a communicating thermostat to a home automation system.

Outdoor Conditions
- View the current weather conditions or, in some cases, a weather forecast for the week — just for grins or for advanced control of the indoor environment. Many smart thermostats pull this information from weather-oriented web sites.

Anatomy of a smart thermostat system: Click to enlarge

- Outdoor temperature and humidity sensors can tie into most smart thermostats.

- Sync the outdoor weather conditions with the indoor temperature setting. For example, if the morning temperature is cool, but the day will be a scorcher, the thermostat can start cooling the house before the searing heat kicks in.

- Eliminate condensation of the windows. Indoor humidity can be better controlled by having a smart thermostat self adjust according to the weather outside.

- Select a thermostat that is compatible with your heating, ventilation and air conditioning system. Different thermostats are required for “multi-stage” heating and cooling units. Check also for compatibility with humidification and dehumidification systems.

- The thermostat communicates with some type of interface device connected to your HVAC equipment. Some smart thermostats can simply replace your old thermostats using the existing wiring; others require additional wiring; and others may communicate wirelessly with the HVAC interface.

- In the event that the “smart” features of a thermostat or automation system fail, the HVAC system should still continue to work as usual.

Home Automation
- Include the thermostat in your automation system’s lifestyle modes, such as GOODNIGHT, VACATION, or PARTY to enhance comfort and energy savings. These modes can be triggered by a button press on a keypad, iPhone, touchscreen or other interface. Or they can be programmed to launch automatically so that, for example, the temperature starts to rise 30 minutes before the “wakeup” scene.

- The HVAC system can respond automatically to a specific event, such as a fire. In that case, the system fans could be shut down to prevent the spread of smoke and flames. Or if the house gets too hot or cold, the system could activate back-up air conditioners or heaters in temperature-sensitive rooms.

- Some thermostats can respond automatically to changes in the energy rates and other parameters set by utilities. With a home automation system, however, more devices, such as energy-guzzling lights and major appliances, can react to utility adjustments.

- Add motion sensors to the system so that the temperature adjusts automatically in the event of activity or non-activity in the area. Generally, the same motion sensors used by your security system can double as occupancy sensors for your HVAC system.

Utilities & Smart Grid
- Smart thermostats connect to the utility either directly via the Internet, radio waves or some other long-distance technology; or they can connect via a smart meter, which then communicates through any number of platforms.

- The most basic smart thermostats do little more than display information from the utility, such as the price of energy at any given moment, your current electric bill, or your energy usage for the day, week or month. Homeowners must then take it upon themselves to react to the information.

- More advanced thermostats can respond automatically to information from the utilities. For example, the temperature may rise or lower a few degrees based on the price of energy or in response to grid overloads. Usually, homeowners can manually override any automatic setbacks.

- Many utilities now offer free or discounted smart thermostats in return for your participation in their energy-management initiatives.

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Julie Jacobson - Editor-at-large, CE Pro
Julie Jacobson is co-founder of EH Publishing and currently spends most of her time writing for CE Pro, mostly in the areas of home automation, networked A/V and the business of home systems integration. She majored in Economics at the University of Michigan, earned an MBA from the University of Texas at Austin, and has never taken a journalism class in her life. Julie is a washed-up Ultimate Frisbee player with the scars to prove it. Follow her on Twitter @juliejacobson.

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