Hi all—
This week, I took a deep dive into the exciting and controversial world of thermostat settings. If you have a thermostat, you've probably gotten into a fight over where it should be set. Outrage over a rumored recommendation that it should be at 82ºF while you're sleeping recently got me thinking about what the right number would be to save money and stay cool. It turns out my default setting of 72ºF is not it.
I've excerpted my full story on beating the heat without destroying the planet below. Click here if you want to read the full version on Vox.
Happy Fourth of July!
Adam Clark Estes, senior technology correspondent
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Let's settle the debate over thermostat settings
Micah Pollak had no idea the trouble he was getting himself into when he shared his preferred thermostat settings on social media. “I just discovered most of our friends set their AC at 68º-73F during the summer,” Micah, who is an economist at Indiana University, posted on Threads in late June. “We keep ours at 77-78F. Are we monsters!?” Nearly a thousand replies later, the consensus was that, yes, Micah’s family are monsters, probably some type of lizard.
Although he didn’t realize it, Micah has been following a set of numbers from the Environmental Protection Agency that tends to spark an internet freakout every summer, often after a local news station does a segment on how to reduce your energy consumption and lower your utility bills. The recommendations include keeping your thermostat at 78º degrees when you’re at home during the day, 82º at night, and 85º when you’re away during the warm months.
To many people, sleeping in 82º heat is simply outrageous. (Not to mention terrible for your sleep, according to experts.) But energy prices are crazy too, and they’re only expected to rise as utility companies spend more and more to make the grid more resilient to the effects of climate change. Extreme weather events are becoming more common, and heat waves in particular can strain the power grid, especially when thousands of people are running their ACs at full tilt.
So maybe cranking up your thermostat isn’t such a bad deal. Typically, I’m inclined to set my AC to 72º on a really hot day. If I could get used to a balmy 78º degrees inside, I’d not only save money, I’d be doing my part to keep the grid running smoothly so that everyone can enjoy a little bit of air conditioning, too. And the savings are real. The EPA says that for every degree warmer you set your AC, you can save 6 percent on your cooling costs, although you get diminishing returns as you go higher and higher. Put simply, if your cooling bill is usually $170, setting your thermostat a single digit higher will save you over $10 a month.
There’s one big problem, though. That 78º baseline isn’t a real federal government recommendation. The EPA’s Energy Star program does have a guide for programmable thermostat settings, but it doesn’t recommend a specific number to set your thermostat to in the summer. The numbers that show up in the news actually come from a table in a 2009 document that offered examples of what energy-saving settings could look like.
“Your household temperatures are very much a personal choice, and ultimately people should do what makes them comfortable,” Leslie Jones, a public affairs specialist from Energy Star, told me.
The agency’s official position is that you can save “up to 10 percent on heating and cooling settings by simply turning your thermostat 7°-10°F for 8 hours a day from its normal setting.” In other words, if you keep it at 71 while you’re home, go ahead and set it to 78 if you leave for the day.
Then again, setting your thermostat at 78 degrees at all times is not a monstrous idea. And setting it at 72 degrees probably means you’re wasting some energy.
Nobody wants the government telling them to suffer more in the summer heat. A lot of our assumptions, though, about how air conditioning works, how to optimize the effectiveness of this century-old technology, and how to save energy in the process are just that: assumptions. To clear up the outrage over where we set out thermostats, I talked to experts in thermal comfort, HVAC technology, and the built environment.
It turns out, some of the most effective ways to stay cool are both simple and cheap.
Why we fight over the thermostat
It’s a time-honored American tradition to fight over the thermostat. Winter, summer, spring, and fall, any given home will be too hot or too cold for someone in the family.
This is for good reason, too. Physiologically, we each have our own optimal thermal comfort level. It comes down to a few key factors, according to Boris Kingma, a human thermal performance researcher at the Netherlands Institute of Applied Technology (TNO). The environment, including temperature, humidity, wind, and solar radiation, is obviously the big one. If it’s hot outside, you’ll feel hot. But a person’s metabolic rate and general physiology, including age and overall health, also play a big role — as does the clothing you’re wearing.
Metabolism is what’s at play when you talk to people who say they “run hot.” They might literally do that if they have a high metabolism, which causes your body to produce more heat. People with more muscle mass, for instance, tend to have higher metabolisms, retain heat, and prefer cooler temperatures. The opposite goes for people with lower metabolisms, who lose heat and might need to wear a sweater in their over-air-conditioned office. Our metabolisms decrease with age, which might be why you think your grandparents keep their house too warm.
It is therefore difficult, if not impossible, to find a single thermostat setting that will make all of America happy. Heck, it’s hard enough to agree on anything in a single family. But the good news is that our bodies are very good at acclimating to new environments. Kingma told me that it only takes about 14 days for your body to adjust to a new baseline temperature. So if you’re used to New York City’s relatively mild summer average of 80°F and then move to Miami, where it’s closer to 90°, you’ll probably get used to it.
The same holds for thermostat settings. If you do try and save some money by moving your thermostat one digit up, your body will adjust in a couple weeks, especially if you use a fan and wear lightweight clothing inside. Fans are especially effective, since they move air around your skin, helping sweat evaporate. Loose clothing has the same effect.
“Many of the solutions to this particular problem don’t need to be high tech,” said Kingma. “Dealing with temperature is about as old as humans.”
The role of evaporation cannot be overstated here. Sweating cools us down because the fluid on our skin evaporates and helps us shed heat. This explains why humidity is so miserable: The air is already so saturated with moisture that your sweat doesn’t evaporate effectively, which means you don’t cool down as easily. On windy days or in dry climates — a dry heat, if you will — sweat evaporates more readily, making it easier to stay cool. Fans can help in either scenario.
Focusing on reducing humidity is actually how we got air conditioning in the first place. In 1902, an engineer named Willis Carrier installed an “apparatus for treating air” at a printing company in Brooklyn that was having problems with magazine pages wrinkling in the summer heat. The machine sent air through coils filled with cold water, which removed humidity from the air and cooled the room. It wasn’t until 1922 that the Carrier Air Conditioning Company of America introduced the first practical centrifugal refrigeration compressor that would become the foundation for modern air conditioners.
Most AC units today do the job with three simple steps. They pull warm air out of the room, cool it down by running it over coils filled with refrigerants, and then pump the cold air back into the room while releasing the heat to the outside world by using a compressor, which is why your AC can sound like a starting car. Heat pumps, which can heat and cool a home, operate using the same principles when cooling — more on that in a minute.
Air conditioning is an energy-intensive process, and the refrigerants used in them present a few problems of their own. The most common refrigerants needed to make these machines work include chlorofluorocarbons (CFCs) and hydrofluorocarbons (HCFCs), commonly known as “freon,” which are greenhouse gasses that deplete the ozone and contribute to climate change. The EPA has been banning many of these chemicals in recent decades to comply with the Montreal Protocol on Substances Depleting the Ozone Layer. However, many modern replacements that do not damage the ozone are still potent greenhouse gasses.
In other words, air conditioning has historically been great for comfort but bad for the climate.
Not only do they require a lot of energy, which may or may not be supplied by fossil fuels, but most air conditioners also pump more greenhouse gasses into the atmosphere. ACs can keep us cool, but they’ll also warm the planet in the process. It’s a real paradox.
Technologies like heat pumps promise a greener future for heating and cooling, but it will take years to update our HVAC infrastructure due to the cost and sheer scale of trading old, inefficient equipment with new systems. And for many, including renters and certain businesses, those upgrades may even be impossible. So for now, the fight over the thermostat continues.
Read the full story on Vox
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