Smart thermostats can change the temperature in any given room, just like regular thermostats.
Where they differ, however, is in how they operate.
These smart devices are designed to learn our habits and adjust accordingly.
But can they automatically adjust along with a room’s occupancy rate?
A smart thermostat can detect room occupancy using motion and door sensors, which are designed to pick up on the number of people entering or leaving a room. These systems also use passive infrared sensors to monitor the temperature of a room, assessing its occupancy to help keep the area ambient.
This article will explain how smart thermostats work and touch on how you can save money by investing in a smart thermostat to pair with your HVAC system.
How a Smart Thermostat Detects Room Occupancy
If you live in an area where it tends to get a little humid, such as Florida, you’re probably used to big air conditioning units pumping out cold air to your home.
Similarly, in the Great White North, heating in every room of the house is essential.
However, you don’t often need to heat or cool every room of your house all day and night.
In fact, while you’re at work or school, you’d be wasting money to have hot or cold air blowing all day.
Smart thermostats can save homeowners and business owners money on their heating and cooling bills throughout the year by reducing energy usage when occupants are away or sleeping.
You may also wonder: Will a smart thermostat work without Wi-Fi?
Like many of you, I live in an area where the weather is relatively hot in the summer and cold in the winter.
Leaving my home thermostat at 73°F (22.77°C) throughout the summer can end up costing a lot of money.
While I could set the thermostat to different temperatures at various hours of the day, such a process is cumbersome and not consistently effective.
A smart thermostat will automatically turn off the system when no one is home and slightly raise the system temperature to 75°F or 76°F (23.88°C or 24.444°C) when everyone in the house is sleeping.
In turn, it won’t be working quite as hard, which is less energy-intensive.
They achieve this with a number of occupancy sensors, designed to detect when someone is home and in need of warm or cool air.
Smart thermostats use occupancy sensors to determine whether the people living in a house are present and awake, present and asleep, or not home at all.
Modern systems use a combination of motion sensors, infrared sensors, and door sensors for this purpose.
Motion and Door Sensors
Motion sensors and door sensors determine when a person walks into or out of a room. The sensors also know when the occupant leaves the house through the front door.
These are essential, especially in larger houses with less-used rooms.
For example, a person working from home may need multiple rooms to stay cool/warm throughout the day.
In contrast, your bill will be far less should the system automatically reduce consumption when you leave the house.
These sensors can detect room occupancy by picking up on the comings and goings of multiple people through doorways.
Measuring the temperature of a room allows the thermostat to know whether someone is occupying that area.
Thermostat systems use infrared to detect body heat changes. Such sensors can also determine if the people in a room are awake or asleep.
If the temperature of a room increases, the system knows if 1 or multiple people are present.
As people leave the room, its temperature drops and the system can adjust the thermostat accordingly.
Infrared sensors can help detect room occupancy by how much the room temperature increases when you enter, along with how fast.
1 person will heat up a room far slower than 4 or 5 people, for example.
The Best Thermostats and Sensors for Detecting Room Occupancy
Not all smart thermostats are created equal.
With that in mind, I’ve come up with a few of the best thermostats and sensors for detecting room occupancy from Amazon.com:
- Ecobee3 Smart Thermostat: This is an outstanding option for any homeowner hoping to save money on energy bills. Ecobee3 comes with 3 temperature and occupancy sensors, and the thermostat helps manage hot and cold spots. It also claims to save up to 23% on heating and cooling bills.
- Ecobee Remote Sensors: If you choose the Ecobee3 but have a large home, you can order extra sensors for the system. The Ecobee Remote Sensors are sold in a pack of two, allowing you to add up to 32 room sensors to your system.
- Google Nest Learning Thermostat: Another appealing option is the Nest Learning Thermostat from Google. The Nest Learning is Google’s third-generation smart thermostat, featuring Wi-Fi integration, energy savings, temperature sensors, and wireless connectivity.
- Google Nest Temperature Sensors: 1 of the downsides to the Nest is that Google only offers a single sensor within the thermostat bundle. Still, buyers can purchase additional sensors in a single or three-pack, depending on how many rooms they want the system to monitor.
The Ecobee3 uses both motion and temperature sensing to regulate the temperature in a home, while Nest Learning uses temperature sensors alone.
Nest Learning also has a much lower limit on room sensors, maxing out at six.
Controlling Your Smart Thermostat
The earliest smart thermostat models had a significant flaw – they were too aggressive in turning off the system.
In this case, when a homeowner stepped out of their house for a few minutes – to get the mail or drop the kids at the bus stop – the system would have turned off completely.
Though this isn’t the end of the world in mild climates, if you live in Alaska, the last thing you need is for the heat to shut off sporadically.
Researchers created a Hidden Markov Model, or HMM, to combat this issue.
The HMM estimates the probability of the home being in either of the following states: away, awake, or sleep.
Smart thermostats assess the home’s condition every 5 to 10 minutes and use historical data, sensors, and programming to best estimate the ideal temperature setting.
Systems that feature the HMM only shut off if the occupants leave for an extended period.
Pre-Heating and Pre-Cooling for Maximum Comfort
One of the critical features of these units is their ability to tap into historical movement data to understand when the people in a house are likely to come home each day.
Such a feature enables the system to pre-heat or pre-cool the home for a few minutes before the occupants arrive.
Smart thermostats start by slowly pre-heating or pre-cooling the home 10 or 15 minutes before historical data indicates a homeowner’s arrival.
The system does this using slower, high-efficiency methods.
If the homeowner arrives a few minutes ahead of schedule, the system quickly switches to a high capacity and low-efficiency mode to speed up heating or cooling.
Similarly, if more people enter the house (or specific room), the system will adjust and work a little harder to ensure the room is at an appropriate temperature.
Why Invest in a Smart Thermostat?
You should invest in a smart thermostat because heating and cooling make up about 48% of the energy use in U.S. homes. These devices can help you save money without sacrificing comfort and convenience, and smart thermostats with room detection capabilities offer a 20-30% reduction in energy usage.
Elahe Sltanaghaei and Kamin Whitehouse from the University of Virginia state that lowering heating and cooling usage while sleeping can reduce energy usage by roughly 20-30%.
Such savings not only translate to significant cost reductions for homeowners, but they also translate to lower pollution levels.
A 20-30% reduction of energy usage would reduce the emission of air pollutants in America by roughly 1.2 billion tons every year.
Reduced Energy Bills
A homeowner who spends an average of $100 a month on heating and cooling could bring down that expenditure to $70 or $80.
Such savings add up to $240 to $360 of savings per year.
Given most smart thermostats are in that price range, a homeowner could cover the cost of the thermostat and sensors with 1 year in energy bill savings.
They would then profit from that investment for many years as they continue to save on electricity and gas bills.
Easy to Control
Smart thermostats offer other benefits aside from automatically tweaking home temperature.
Most systems include integration with your computer and/or smartphone, allowing you to easily adjust the system throughout the day.
I can recall countless occasions where I left the AC running for an extra hour or 2 because I didn’t want to get up and adjust the thermostat.
Or worse, I’ve spent the night away and left the air running for hours with nobody home to benefit.
With a smart thermostat, I can tweak its settings from my phone.
This is incredibly convenient should you go on vacation.
When certain homes are exposed to extreme temperature spikes and drops, it’s necessary to have the air running to prevent damp/mold (humid climates) or frozen pipes (in frigid climates).
With a smart thermostat, you can control the settings even if you take a winter-warming vacation to get away from the cold.
Smart thermostats are an essential investment for homeowners who rely on HVAC systems to heat and cool their homes.
Rather than depending on a rigid timetable of temperatures for various stages of the day, a smart thermostat activates when it detects higher room occupancy in your home.
Using an HVAC system with a smart thermostat allows you to remain comfortable all year while conserving energy when you are not home or asleep.
The initial investment in a smart thermostat may seem daunting, but you make back that money within months and then continue to save for years.