The house in New Jersey came with a menagerie of control panels. Pallid little rectangles with fuzzy LCD screens, of varying brands and designs. Some were decades old, and there were six of them in total, dotted around various rooms. Joe Truncale, a customer engineer at Google, remembers trying to get his head around the system when he moved in two years ago.
Each thermostat had a piece of paper sticky-taped to it, with a helpful scribble from the previous homeowner explaining how to operate the gadget. Not exactly an intuitive user experience. And it wasn’t economical, either. In one area the heating was running constantly. Truncale balked at the idea of trying to fine-tune each of the fiddly little thermostats. “That’s when I started to think … maybe I build my own,” he says.
So, in a quest for control, he ripped them all out. It wasn’t long until he had built a smartphone app and hooked up a device to his gas furnace that allowed him to control the delivery of hot water to his heaters remotely. Temperature sensors replaced the old thermostats. These tracked the temperature in various rooms and sent that data along wires running inside the walls back to a central hub. With some programming and scheduling, Truncale soon had a system that managed the heating more or less automatically.
He called it ThermOS and made the code open source. “It’s been going since February of 2021,” he says. “I haven’t touched it in over a year. I haven’t made a code change.”
Most people, no matter their skill set, know what it’s like to do battle with a heating system, to wrestle with a thermostat. But even if you don’t want to build your own, there are ways of mastering these gadgets. This is how to make your thermostat work for you—and not the other way round.
Hot Enough for You?
For many, the biggest decision is what room temperature to choose when you’re at home. Many people prefer warmth in excess of 70 degrees, but, unsurprisingly, the higher you go, the more money you’ll spend. The World Health Organization suggests 18 degrees Celsius (64 to 65 degrees Fahrenheit) as a minimum in temperate climates. “I did it myself,” says Jo Alsop, founder of the British independent advisory body The Heating Hub. “I got used to a house that was around 18 to 18.5 degrees [Celsius].”
Turning the room temperature down is one of the best ways of lowering your utility bill, suggests Katy King at Nesta, an innovation-focused charity in the UK. She and colleagues have compared the potential savings from turning your thermostat down by 1.8 degrees Fahrenheit (from approximately 68 to 66 degrees) with reducing the time you heat your home for by five hours every week. The 1.8-degree change could save £100 ($126) on an annual bill in the UK, she estimates, whereas reducing heating time only saves £12 across the year.
“It really surprised me when we did this research,” says King. “It’s heating to a higher temperature that really makes a bigger difference.”
Helen Stopps at Toronto Metropolitan University notes that two rooms with the same air temperature can feel different depending on subtle factors. If there’s a very slight draft in one, for instance, our bodies are very sensitive to that, and it can make us want to crank up the heating. Or if we have particularly cold walls, this creates a convective effect, and, again, that movement of air makes us feel less cozy. Humidity has an impact too—the more moisture in the air, the cooler the room can feel. Using a dehumidifier can help here.
Playing It Smart
Because of the wiring in Truncale’s home, he wasn’t able to easily install an off-the-shelf smart thermostat, such as those from Nest or Ecobee. Smart thermostats have Wi-Fi connectivity and tend to offer a range of automated heating controls. Off-the-shelf models will suit many people well.
“They are way easier to program,” says Stopps, as she explains how having a heating schedule that closely matches the rhythm of your life can impact your utility bill. (Many people heat their homes when no one is there, or when everyone is asleep.) You can set up a heating schedule with many dumb thermostats too—it just takes more input from the user, who must select times when the heating is turned up or down, or make manual adjustments when their plans change.
Smart thermostats, in general, do a lot of this legwork for you by learning or sensing when you’re at home. Truncale has his DIY thermostat connected to Apple’s smart home platform, HomeKit, so that it knows when he or his wife are in the building. It detects when their phones are nearby.
Once set up, the key is to let the automated system do its work. Stopps and colleagues tracked the behavior of 54 smart thermostat users in Toronto for a year and found that the devices were generally effective at managing household heating automatically. However, some people enjoyed overriding their system to boost their heating or to make on-the-fly switches to the schedule. “There was one person who switched 456 times,” says Stopps. “Actually, about 10 percent of participants switched more than 300 times. It’s absurd.”
The risk is that by boosting or raising temperatures hastily, in a rush to get warm, you end up overheating your home, which isn’t very economical. Some studies suggest that this behavior has the potential to undermine the benefits of smart thermostats altogether. However, Stopps and her colleagues found that the smart thermostats in their study remained effective at keeping costs down even when overrides were commonplace.
She says that, generally speaking, if you keep tight control of a heating schedule, you should see noticeable energy savings, regardless of the actual heating system you use—whether you have water-based (or hydronic) heating, forced air, or another technology.
Many smart thermostats offer a range of additional features, including “weather compensation,” which regulates heating in response to the weather. Some, by tracking temperature and humidity changes indoors, can even detect when a window is open and alert the user or shut off the heating until the window is closed.
Tado thermostats, widely available in Europe, are designed to do this. Some users set up their Tado devices to make regular use of smart features and also apply manual adjustments when needed—around 20 percent of users in Tado’s key European markets take this approach, says Dennis Scollar, product manager. “I thought it would be less, to be honest,” he says. “We have a fair amount of pro users that optimized above the average.”
These pro users tend to save 23 percent on their energy bills versus people who don’t have a smart thermostat. Other, less fastidious Tado users save about 20 percent in comparison to those without a smart thermostat, according to data that Tado shared with WIRED.
How Low Can You Go?
A heating schedule that responds to your presence sounds great—but what does that actually mean? Should the heating switch off entirely when you’re away? In many cases, it’s actually better to run your heating constantly but choose “setback” temperatures, say around 63 degrees, when a high level of warmth isn’t required. The timing and level of these setback periods will vary a little depending on your home, how well insulated it is, and the kind of heating system you have. A YouTube video from Heat Geek, a heating industry training and advice service in the UK, explains this in detail.
People might also consider whether or not to “zone” heating in their property. If you’re only using one room in a house for most of the day, it’s perhaps not necessary to heat the whole building to 68 degrees. But in some cases, keeping certain rooms very cool could reduce the overall efficiency of your heating, since those rooms will soak up warmth and make your boiler or heat pump work harder. Selecting appropriate setback temperatures for rooms not in use, for example, could prevent unnecessary losses.
The temperature of your heating system can also probably run lower than you’d expect. With modern gas boilers and heat pumps in particular, the concept of “low and slow” can achieve significant energy savings. In a system that uses hot water to heat up radiators, for instance, this means you would ensure that this water is no hotter than around 113 to 122 degrees Fahrenheit. This is known as the flow temperature, which is completely different from the thermostat temperature, which determines how warm a room is.
How low you can go with the flow temperature will depend largely on your heating system’s design—low flow temperatures work really well with underfloor heating or water-based systems with large radiators, because the expansive surface area helps transfer heat into a room. The amount of insulation in your home will also affect things. PassivHaus properties, for example, which are built to extreme standards of energy efficiency, need little if any active heating.
Alsop says setting a gas combi boiler’s flow temperature to 122 degrees or below will also help save money in a second way, because this makes it easier for the boiler to run in condensing mode, through which it can recover heat from hot gases that would otherwise escape into the air, and therefore use less fuel overall.
Last autumn, the UK charity Nesta launched an online tool to help people work out how to reduce their boiler’s flow temperature. Between October 2022 and March 2023, 214,000 people used the tool and turned their boiler flow temperature down—which would equate to annual energy bill savings of £20 million ($25.21 million), or carbon savings totaling 37,000 tons.
Heated Exchanges
Lower temperatures and careful management of a heating schedule—the theory is all there. But putting it into practice might be more difficult. If there is more than one person in a home, choosing a mutually agreeable room temperature is not always easy. Elderly people naturally feel colder because their blood circulation is lower, among other factors. And research shows that women tend to feel the cold more than men, partly because of differences in their musculature—though there are exceptions.
Thermostats can become flashpoints of “thermal conflict,” says Benjamin Sovacool at the University of Sussex in the UK. He and colleagues have studied the behavior and responses of people living in 100 homes fitted with smart heating technology in the UK. “People were having fights,” says Sovacool. Some complained about being too cold while their partner was fine; others said a family member was wasting money—and harming the planet—through excessive heating. These disputes often represented bigger, deeper problems in those relationships, suggests Sovacool.
And privacy-eroding smart home systems sometimes reveal problematic behavior. You might see that your heating or hot water has come on when you thought your partner wasn’t at home, for example. “I think three of the homes in our 100 homes had incidents of suspected infidelity tracked by the system,” says Sovacool.
If your goal is to run your heating as economically as possible, you’ll have to keep in mind that people can be very particular about the temperatures they will tolerate. Their preferences around such things tend to be “inelastic,” Sovacool says. It is possible to supplement room heating with warm clothes, electrically heated garments or blankets, and other low-cost measures.
Beyond that, Sovacool suggests that giving people a fine-grained level of control over their heating, with the help of a savvy thermostat perhaps, does help to reduce the likelihood of an altercation. There are no guarantees in life, though.
“My partner and I fight over this all the time. I like it about 5 degrees cooler,” he says. “It’s how I’m built, darn it.”
