By June 20, 2016

Time for a Supercool Idea

Photo Illustration By Marius Britt

Photo Illustration By Marius Britt

Experts tell how to run your AC and lower your electric bill. 

By Nadine Shaalan — The old-school energy-saving advice to “set it and forget it” doesn’t lend itself to time-advantage plans—especially here, where summer temps regularly top 110 degrees during peak rate hours, forcing your AC unit to run seemingly non-stop. While some still swear by setting the thermostat at, say, 79 all day and night, others have discovered a method called “supercooling” or “pre-cooling” to bring their power bill way down.

Engage With Your Energy Consumption When we asked APS for the most important energy-saving advice they could give, spokesperson Anne DeGraw said this: “Figure out when, where and how you’re using your power.” APS already has that info and has structured its time-advantage peak rates accordingly. The idea behind supercooling is to shift the cooling of your house—responsible for up to 70 percent of your summer energy usage—to the time of day when energy rates are low.

Rosie Romero, building contractor and host of the KTAR radio show “Rosie on the House,” has been touting the cost-savings of supercooling since APS introduced the preferred-time-of-day rate about 15 years ago. He likens electricity for your home to gas for your car: “If your favorite gas station sold gas at 50 cents a gallon from 7 o’clock at night to noon, and then from noon to 7 they sold gas at $2 a gallon, when would you fill up?” Romero asks.

How Supercooling Works To cool your house using cheaper power, program the thermostat way down overnight and through the morning, and back up when rates go up again.

“I set my auto thermostat for 73 to 74 during those hours and then set it for 90 during on-peak,” said Kristine Parker-Schlitzer who started supercooling her 3,500-square-foot home last year. “It usually gets up to about 84 on a hot day but not until about 5:30 or 6 p.m.” Schlitzer also tries to unplug unneeded appliances and avoid laundry during peak hours. She said this saves her an average of $80–$100 on her monthly bill.


Long-time contractor and radio host, Rosie Romero.

Running the AC continuously for hours is counterintuitive for those who are budget- and energy-conscious, but Romero calls this one of the greenest things you can do. “I get a lot of pushback: ‘You’re just gobbling up power!’ Yea, but I’m gobbling it up when the power company can’t do anything with it. Once electricity is made, you can’t put it in a gas tank and store it,” he said. “If we can take the peak off the afternoon summer load, it’s going to keep us from having to build another power plant for decades. We build power plants to meet summer afternoon peak loads. And then the rest of the time we’re dealing with excess capacity.”   

Travis Ringe of Proskill Plumbing said, despite what many think, running the AC continuously is easier on your system than the on-again-off-again of trying to maintain a steady temperature all day. He takes the car analogy further: “The constant stop-and-go of city driving puts a lot of wear and tear on your car, and decreases the [fuel] efficiency… The air conditioning system is much the same, except the fuel is electric and the vehicle is a trio of motors,” Ringe said.

The goal, Romero said, is to shift your energy usage ratio from 60:40 (off-peak:peak) to 80:20. Given the direction the utility is hoping to go with the new rate structure (cheaper base rate, higher peak rate + demand fee, [see “APS Requests Rate Hike,” In&Out, June 16]), supercooling might become more the norm.

While it feels like gaming the system, APS is on board. “Pre-cooling is part of APS’s plan to educate our customers about how to be energy efficient,” said APS’s DeGraw. “Shifting air-conditioner use to off-peak periods allows customers to take advantage of lower energy costs.”

As with cars, your mileage may vary. If you fling your shutters open and bake bread in the middle of the day, your home will struggle to retain the cool temperature. Factors that affect how well your home holds the temperature and how much you save are many, including the age of your appliances, the construction of your home, how many children/grandchildren/pets you have.

Romero challenges everyone to give supercooling a try. “I will take anyone that says it doesn’t work, I’ll spend five minutes on the phone with them and find out why,” said Romero, who takes listener calls on his radio show. “It works for everyone.”

How to Supercool (Pre-cool) Your House

What You Need

The Right Plan If you use a time-of-use plan that charges less for off-peak usage, you are good to go. If not, switching is easy. Note the times and days when you are charged less for your power. (APS may advise you against switching based on your usage history. But if you are about to start supercooling, your usage patterns are about to change significantly.)

A Programmable Thermostat You can manually set your thermostat twice daily, but a programmable thermostat will make it a worry-free task.


  • If you have a pool, you’ll need a timer for your pump. The pool pump can be the second largest energy consuming item in your home.
  • Timers or switched power strips can help manage devices that don’t need to be drawing power at all times.
  • Optionally, you can get an energy management demand computer that will limit your peak load and distribute your demand.

How it’s Done

  1. Set your thermostat to go as low as your are comfortable—say 68 degrees—when off-peak billing time starts (typically 7 p.m., but depends on your plan). You might have to break out the blankets and sweaters.
  2. Set your thermostat to as high as you are comfortable—say 82 or so—when on-peak billing starts (typically noon, depending on your plan).
  3. Set your pool pump to operate the required number of hours so that it runs only during off-peak hours.
  4. Consider putting a timer on your water heater and other devices to run only during off-peak hours.

Visit where you can monitor your peak vs. off-peak usage by day. Data is updated regularly to within about two days.


Posted in: Home & Garden
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