Ecobee3 Lite Smart Thermostat Install and Review

A smart thermostat is one of the more popular devices people install as they build their smarthome. It can help make your home more comfortable and save money on heating and cooling costs. I recently decided to try out the Ecobee3 Lite smart thermostat and I’m glad I did.

Ecobee3 Lite Retail Box
Ecobee3 Lite Retail Box

Key smart thermostat features

Nest, Honeywell, Ecobee, and many others make smart thermostats with similar features. The key features I was looking for were:

  • Remote management, on and off my network
  • Ability to use a remote room temperature sensor
  • Works with hydronic (radiant) heating systems
  • Integrates well with Home Assistant
  • Ability to view data and reports about my HVAC system

Many smart thermostats do much more than this, but these are the key features I was looking for.

Why I chose the Ecobee

I looked into many models of smart thermostats and narrowed it down to the following manufacturers: Nest, Ecobee, Honeywell and Radio Thermostat. The Radio Thermostat models I looked into were the least expensive but didn’t support remote room sensors. The Honeywell models I was most interested in (Lyrics) require a custom component to work with Home Assistant, and I’m trying to avoid custom components. That left me with Nest and Ecobee thermostats, which are the most popular smart thermostats for a reason.

The feature sets for the Nest and Ecobee Thermostats are similar. One key feature for the Nest is that it will actually learn your heating and cooling patterns over time. This isn’t that important to me as I liked fine-grained control of my heating schedules anyway, plus that feature isn’t as important with efficient, slow recovery hydronic systems like mine. The Nest is also better looking and supports 5GHz Wifi, unlike the Ecobee.

Despite those advantages, I still chose to go with the Ecobee. I could generally find them at a lower cost than Nests, and their energy reports and HVAC usage data blow the Nest out of the water (more about this later in this article). The final nail in the coffin was how the two interact with their remote temperature sensors. The Nest has a much more rigid integration of remote sensor readings into the thermostat schedule (only four different time blocks).

Google recently announced they will end 3rd-party API support for the Nest. I didn’t know that before I made my purchase decision, but I’m glad I went with Ecobee. An accessible API is an important feature for integrating with smarthome platforms.

Ecobee3 Lite vs Ecobee4

With that decided, which Ecobee was the next question. The Ecobee thermostats are the same except for a few differences. The Ecobee4 is slightly bigger and has built-in Alexa, speaker, and mic, which I found appealing. It also works with more types of systems. The Ecobee3 lite won’t work with humidifier, dehumidifier, and ventilator systems. The Ecobee4 also comes with a remote room sensor, whereas the Ecobee3 lite doesn’t come with any, but you can buy them in 2 packs separately.

There is a downside to having Alexa built-in. These thermostats don’t recognize when there is another Alexa powered device listening and thus will respond to commands they hear even when they are meant for another device. I have Echo dots near where these thermostats would be so that means I won’t use that function.

The big thing the Ecobee3 lite has going for it is that it is much cheaper. You can sometimes get it for more than $100 less than the Ecobee4. Since I want three, and I don’t need 3 room sensors, the Ecobee3 lite is the obvious choice for me.

What’s in the Ecobee3 Lite box

What's inside the Ecobee3 lite box
Ecobee3 Lite Box Contents
  • Ecobee3 lite thermostat
  • Backplate for mounting and wiring
  • Power Extender Kit (PEK) for thermostats without a C (common) wire
  • Trim plate
  • Mounting screws and drywall plugs
  • Installation instruction booklet
  • Wire labels
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You can find detailed Ecobee3 lite specs here.

Ecobee3 Lite installation

My house has a hydronic (radiant) heating system. Using PEX (crosslinked polyethylene) tubing in the walls and floors, the tankless water heater pumps hot water into the house to heat it. I have three zones in the house and for each zone, I need to install a thermostat.

The thermostat wiring connects each thermostat to a transformer and relay. When a thermostat needs to increase the temperature for its zone it sends a signal via the relay to the water heater to heat up water. It also sends a signal to the water pump for that zone to pump water. Note that I’m not an expert in these systems – this is my understanding of how they work.

Because my system is heating only, I only have two wires going to my battery powered thermostats. I also don’t have a C (common) wire going to my thermostats to provide constant power.

Adding a C wire

Unfortunately, most smart thermostats need constant power to work due to the demands of the circuitry and WiFi radio. This is usually provided by the C wire. In order to help users who don’t have C wire, Ecobee has a solution where you can use the provided PEK (see “what’s in the box” above).

The PEK is a slick solution. It steals power from HVAC systems to power the thermostat. I would need three PEKs (one for each thermostat) installed in small space (see below).

I decided I’d be better off using the transformer to turn one of the wires going to each of the thermostats into a C wire. This also helps out if I ever want to use a different smart thermostat in the future. Additionally, I don’t think the PEK works with two wire systems.

Relay Wiring before ecobee3 lite
Initial wiring. Red goes to relay, white goes to blue 24V output of transformer.
Thermostat wiring at power
Closeup. I’m going to use blue thermostat wire as C wire.

The transformer connected to my relays can provide the voltage I need to create a C wire. Extra wiring to thermostats exists (in the brown insulation), just not connected (this is common). I will connect the blue thermostat wire to the yellow wire from the transformer, which will provide the 24V common voltage. This turns the blue thermostat wires into a common wire.

Updated relay wiring with common wire for ecobee3 lite
Blue is now common (C wire)

Connecting the thermostat to the new wiring

Note I also swapped the red (R) and white (W) wires coming from the thermostat. I’m used to the W wire going to the relay to call for heat, and red going to 24V to power the circuit. I could have left it the way it was, but I wanted the white cord to go into W terminal on the Ecobee and red to go into the R. Now my 2 wire system is a 3 wire system with a C wire that I can wire up to the thermostat as shown in the picture below:

Wiring at the thermostat
Wiring after adding the blue C wire I connected at the transformer

After that, I just popped the Ecobee in. The Ecobee has a couple of different mounting options. You can just use the backplate. Alternatively, the trim plate is helpful if you need to cover up blemishes left by your old thermostat (which I needed). It is paintable.

Ecobee3 lite Thermostat fully installed
Installed thermostat with trim plate

Using the Ecobee3 Lite

Setup and usage is pretty straight forward. The thermostat walks you through the setup and most functions can be done from the web, app or directly from the thermostat.

Ecobee web interface
Ecobee Thermostat Web Interface

Ecobee3 Lite initial setup

The first time you power up the unit it will ask you to confirm what type of HVAC system you have (which it determines from the wires connected to the thermostat). Then it will ask you for the information needed to connect to your wifi network. After that, it asks you for information it needs to run correctly, like your country and time zone. Then it gives you the code you need to register your thermostat online (from the app or on the web). You’ll need to create an Ecobee account. Then you’re done and ready to use it.

Ecobee app interface
Ecobee App Settings

Thermostat display

The thermostat is a touchscreen that is perfectly lit. It’s not too bright, and not too dull. You can easily see and use it in the dark or during the day. The screen is responsive and allows you to easily control almost all the features of the unit (schedules, temporary settings, network connectivity, etc.). The display only shows temperatures rounded to whole percentages.

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Additionally, you can check the weather forecast. You can set up security to restrict what unauthorized users can change via the thermostat display.

Comfort settings and schedules

Ecobee uses comfort settings to designate temperature and fan settings for different circumstances. By default, you have an Away setting, a Home setting, and a Sleep setting but you can define more if you’d like. When creating a schedule you associate times of the day with the comfort settings and that tells the Ecobee what temperature you want your home to be. The nice thing is that you can just change the comfort setting and then any part of your schedule that uses that setting will automatically update to your new comfort settings.

Schedules are very flexible. You can define comfort settings in 30-minute increments and have different schedules for each day of the week.

Reminders and alerts

You can set up reminders via the app or the web interface. Reminders let you know if you need to service your HVAC system. They also can let you know when you need to do periodic maintenance, like furnace filter replacements, UV lamp cleaning and replacement, and general HVAC servicing.

You can set up alerts in addition to reminders. Alerts let you know if your heating or cooling equipment isn’t performing right. As you can see below, I’ve set up alerts for when the temperature gets too low or high. Additionally, you can set up alerts for humidity levels.

Ecobee3 lite alert settings
App Alert Settings

Vacation Mode

I love the vacation mode. I no longer have to remember to change my thermostats scheduling before and after my vacation. With vacation mode, I can schedule this behavior. For example, I can set when the vacation starts, when it ends, and what temperature the house should be kept above while on vacation. Brilliant!

Ecobee Vacation Settings

Ecobee3 Lite data about your HVAC (Home IQ)

Ecobee’s “Home IQ” allows you to see how your HVAC system has performed over time. Additionally, it provides information about how efficient your system is and how it compares to similar HVAC systems.

System tab

Ecobee3 lite stats
Home IQ System Screen

The System tab provides an overview of your equipment runtime, as well as snapshots at particular times. Bars at the top show when your system was heating or cooling. The bars below compare the desired temperature (based on your comfort settings and schedule) with the actual indoor temperature and the outdoor temperature.

This chart can show you how often your system is running and how long it takes to heat or cool to desired temperatures. It can also show how outdoor temperature affects your HVAC system. In addition, you can view your home’s relative humidity levels over time.

Schedule tab

Ecobee3 lite schedule stats
Home IQ Schedule Screen

The schedule tab allows you to see your system runtime relative to your schedule. This chart shows how indoor and outdoor temperatures relate to the setbacks and comfort settings. You can see how long the thermostat is predicting it needs to run in advance of a change in comfort setting in order to reach the desired temperature at the desired time.

Weather Impact tab

Ecobeee 3 lite Home IQ Weather Impact Tab
Home IQ Weather Impact Screen

The Weather Impact tab helps you to understand how weather influences your HVAC runtime. In turn, this helps you understand how weather affects your energy bill. It shows you how long your HVAC system runs each day plotted along with the average temperature that day.

Runtime Report tab

Home IQ Runtime Report
Home IQ Runtime Report courtesy of

This is a monthly report that shows you the total runtime of your HVAC system during the previous month. It compares how your system ran to how much it would have run if you kept your system running at 72 degrees. It estimates your savings in terms of dollars and runtime. You only get this report once a month.

Community Comparisons tab

Home IQ Community Comparisons Report
Home IQ Community Comparisons Report courtesy of

This tab shows you the total runtime savings compared to the average savings in your state. The report also provides a breakdown of how much your comfort settings are affecting your savings. This report is generated only once a month.

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Home Efficiency tab

Home IQ Home Efficiency Report
Home IQ Home Efficiency Report courtesy of

This is a simple bar graph that compares your home’s efficiency to other homes in your state. It shows how well your house retains its thermal energy. If your house does this well, your HVAC system doesn’t need to work as hard to reach the desired indoor temperature. This is another once a month report.

Additional observations about the Ecobee3 Lite

There are a few other things to know about the Ecobee3 lite:

  • There’s no backup battery. If your power is out, the thermostat won’t work. Not too big of a deal, as your HVAC probably won’t work either.
  • I purchased additional room sensors, which also have occupancy sensors. They were easy to pair with the thermostat and allow you to use the remote temperature or average the remote and unit temperature for use as the overall temperature. You can use the sensors to override comfort settings if it determines you are home or away when you normally would not be.
  • If for some reason you lose network or Internet connectivity these thermostats will still function as a dumb thermostat.
  • Make sure you have a strong WiFi signal where you are placing your thermostat.
  • Integration with Home Assistant was easy. Although the thermostat display only shows whole number temps, the API provides temps to the 10th of a percent, which I can see in Home Assistant. I can also see the temps and occupancy status of connected sensors via Home Assistant.
  • The Ecobee3 Lite allows for temperature calibration in case the temperature is consistently reading too high or low. Similarly, you can calibrate the humidity.
  • You can also adjust the temperature differentials (defaults to .5 degrees Fahrenheit). This determines how far away from the desired temp the thermostat will allow before it turns on heating or cooling.
  • There is an adjustable minimum on time which defaults to 5 minutes. This prevents short cycling your HVAC system.
  • There are third-party trim plates if you don’t like the provided one or just want a different look.

Final Thoughts

As you can see, this a powerful thermostat that provides tons of data for geeks like me. I’ve had these units for a couple of months and I am extremely happy with my decision to purchase. If you’re in the market for a smart thermostat I highly recommend you give the Ecobee3 Lite strong consideration. It makes a great addition to the ultimate DIY Smarthome.

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Ecobee3 Lite Smart Thermostat Install and Review

by HomeTechHacker time to read: 10 min