Your AC will actually run longer overall if it is left on all day instead of being shut off. If you turn it off for part of the day, it runs less and results in more energy savings for you. In almost all cases, it will save you money to shut off your AC while you are away from home.
Turning Your Air Conditioner On & Off vs.
Since air conditioners use more energy when they cycle all day, it is cheaper to let your system operate at full capacity when you're home instead of running it at a lower capacity all day. The more energy you use, the more money you'll pay in monthly utility bills.
As a bonus, by simply turning your thermostat down 10 degrees, you can save roughly 10% on your electricity bill annually. Not bad!
If You're Leaving Home for the Day or Weekend ...
"It's more energy efficient to keep the unit on but turn the temperature setting up," she advises. Turning off the AC unit during the day is not necessarily a bad thing — it is a myth that the AC unit has to work extra-hard to cool off a hot house.
Turning off your air conditioner during the day will certainly conserve energy, but problems arise when you get back home and turn your system back on. If you leave your air conditioner off during the day, indoor temperatures will continually rise while you're gone.
Related Story. It may seem like a waste of energy to turn your A/C on and off, but doing so actually saves you a fair amount of money, Amann says. "Air-conditioning systems run most efficiently when they're running at full speed," she explains.
The short answer is, yes. Turning your AC on and off periodically will waste energy, as opposed to leaving it on all day and bumping up the temperature when you're not at home. That's because more energy is required to reach a thermostat setting after the system has been turned off and back on.
Turning your air conditioner in and off forces it to run at lower speeds for shorter periods, which ends up worse for you because now you have both a hot house and a high energy bill. It also adds extra strain on your unit, which can age it prematurely, resulting in you needing an emergency AC replacement.
Studies have shown that, on average, shutting off your air conditioner at night will reduce your total cooling costs by somewhere around 30% compared to leaving it turned on 24 hours a day.
You can save as much as 10% a year on heating and cooling by simply turning your thermostat back 7°-10°F for 8 hours a day from its normal setting. The percentage of savings from setback is greater for buildings in milder climates than for those in more severe climates.
Energy Saver recommends setting your air conditioner to 78 degrees when you wake up, 85 degrees during the day, and 82 degrees when you're sleeping to save the most money.
According to the Department of Energy1, 78° Fahrenheit is the sweet spot for air conditioners to balance energy savings and comfort when people are at home and need cooling.
Choosing the Auto Setting
If you set your preferred temperature very low, your air conditioner is still going to run longer than necessary. But using the AUTO setting with a reasonable set temperature will keep your energy costs low, especially if you turn your unit off when you're away from home or asleep.
It is safe to do so, but regular maintenance is even more important because there's more wear and tear on the system. Many people believe it's more efficient to run your air conditioning all day. This is because the unit will never have to work too hard at any given point to cool the home.
It is highly recommended that you close all windows and doors when the air conditioner is turned on. This will keep the cool air inside the room and keep the temperature moderate. In addition to cooling efficiency, leaving the windows open will also put stress on the air conditioner.
Conclusion. For most homeowners who are going on vacation for a week or two, it's probably best to keep your air conditioner on. But there's no need to cool your entire home the same way you normally do—so turn your thermostat up. If you use a programmable thermostat, look for a vacation, hold, or away function.
During peak hours your electrical company may be charging you 24 cents per kilowatt per hour, and then as low as 4 cents during off-peak hours. The real question is, why pay 24 cents when you can pay 4 cents? Running your air conditioning during off-peak house lets you run it for much longer—and cheaper.
It's not too great for the environment, either, and you could quickly wear down your air conditioner and require a replacement before you know it. From time to time, it's important to give your air conditioner a break. Let the components have a rest so that you can keep your equipment longer.
Ideally, a properly operating air conditioner should cycle for roughly 15 to 20 minutes, two to three times per hour. If the temperature inside your home is very high, is much higher than the temperature that your thermostat is set at, or the outside temperature is very high, the run time will increase.
Most of the Time, Aim for A 15 Minute Cycle
Ideally, your AC should run for 15 minutes on nice, warm days. Only on those rare triple-digit temperature days should your air conditioner be running almost all the time. If your AC isn't following this pattern, you could have a problem.
Your AC has more capacity and is more efficient at night when it's cooler than it is during a hot afternoon. That's why HVAC designers are always aware of the three types of heating and cooling loads.
As long as the air conditioner filters are properly fitting and clean, and the HVAC system is in good condition and the thermostat is set properly so that the unit turns on and off throughout the day – it is safe to leave an air conditioner on all day. This is true for a central air unit or a portable air conditioner.
Modern air conditioning units are designed to run 24 hours a day. There is no harm in having it run to keep your home cool all day long. If you wanted to, you could have your AC unit running 24 hours a day, seven days a week.