Heat waves have swept through much of the U.S. already this summer, breaking temperature records, straining power grids and buckling roads.
And a long-lasting heat dome is set to bake much of the country's midsection in triple-digit temperatures in the coming days, according to AccuWeather.
And when the heat is on, so are the air conditioners. In late June, when parts of the country were under a heat dome, searches for the term "precooling" spiked on Google.
The idea calls for significantly lowering your home's temperature during off-peak hours and letting the cool air get you through peak hours when the sun is highest and energy is more expensive.
But does it work? Yes, no or maybe — depending on whom you ask. But don't worry, we also have some other tips to keep you cool this summer.
A researcher has caveats
Researchers have long pondered how to make people less reliant on air conditioning systems, including Daniel Barber — a professor of architecture at the Eindhoven University of Technology in the Netherlands.
He and his students have investigated things like better ventilation strategies and the redesign of buildings. When it comes to precooling — sometimes referred to as super cooling — Barber said it could be a good place to start, with some caveats.
"Running an air conditioner at 60 degrees is going to be pretty energy-intensive, and also produce a lot of HFCs, so there's serious costs associated," he said.
HFCs refer to hydrofluorocarbons, a type of greenhouse gas. But Barber said super cooling could be effective if you take good care of your air conditioning system and keep the windows and curtains closed.
If nothing else, Barber said, don't keep switching the AC on and off if you're trying to be energy-efficient.
"It's a lot of energy to get it started, to cool the room once it's already hot," he said. "The thing to keep in mind is that air conditioning doesn't make the room cool. It just moves that hot air out. So if it's hot in the room, you're giving it a lot of work to do."
What the power companies say
The Department of Energy recommends a starting indoor range between 75 and 78 degrees to save energy during summer days. Opinions on precooling vary among power companies.
Arizona Public Service generally agrees with the idea. It suggests customers who want to lower their bills drop their thermostat's temperature in the morning, raise it during peak hours from 4 p.m. to 7 p.m., and after that, set it how you like.
Georgia Power, the state's largest electric utility, encourages its customers to use less energy during its peak hours of 2 p.m. to 7 p.m. But it said a home would need to be extremely efficient for precooling to work and noted there isn't a concrete range of temperatures that will make the method most effective.
"It would be very dependent on the efficiency and size of the home, the outside temperature, the temperature at which someone is comfortable, etc.," Georgia Power spokesman Matthew Kent told NPR.
And Exelon Corp., which operates six power companies in the mid-Atlantic, says super cooling can actually be more expensive.
"Running your thermostat at its lowest settings, even during cooler temperatures, could lead to excessive energy use and strain on home systems, ultimately increasing costs and creating potential safety risks," company spokesperson James Gherardi told NPR in a statement.
Other energy-saving tips
Ultimately, Barber said changing the thermostat throughout the day could be a big adjustment for those who typically keep it at a set temperature.
Instead, he recommends concentrating cool air in a couple of areas of the home by using fans, certain programmable AC units or in-window units, and spending your time in those parts of the home during peak hours.
And while there is no consensus on precooling, the sources for this story did agree on several other tips that can make cooling your home more efficient, and in turn, more affordable.
They include:
- Changing air filters regularly
- Cutting off drafts in the windows and doors of your home, using things like caulk or weather-stripping
- Using large, heat-generating appliances, such as ovens, dishwashers and clothes dryers, during off-peak hours
- Keeping curtains and blinds closed during peak hours
- Programming your AC system to increase the temperature in your home when you're not there
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