Should You Turn the Central AC Off When Leaving the House?

People who leave the house for the day to go to work or run errands, or leave for an extended time on vacation, may wonder if they should turn off the AC when they are out. Many people think doing so makes sense and will save energy and save money; after all, why fully cool a space when you’re not there? Isn’t that wasteful?

In a word, no! The notion that turning off the air conditioning when you are not home is a good idea is a big misconception that leads to higher energy bills. While turning it off and on might seem like a way to conserve energy, the AC uses more power to start up and cool the space than it does to maintain a consistent temperature. Therefore, leaving your air conditioner on all day, especially on hot days, is generally more energy-efficient and can even save money in the long run.

Maintaining a cool temperature continuously:

• uses less energy than repeatedly cooling down a hot space
• avoids unnecessary wear and tear on components, which could lead to more frequent repairs and replacement
• helps control the indoor humidity level (high humidity=higher temperature feel=temptation to “crank up” the AC)

Keep the AC on when you’re gone

Whether you leave the house for the day or for vacation you should not turn off the AC system. By turning it off, this allows heat and humidity to repenetrate the space which the system is keeping conditioned. This in turn makes the unit work harder to recondition (cool down) the space, resulting in a higher utility bill.

Instead, the best thing to do is set the temperature a few degrees above your everyday desired temperature.

For example, if you generally set the thermostat at 72 degrees during the summer to keep your indoor air at a comfortable temperature relative to the outdoor temperature, try raising it between 75 and 78 degrees. This will avoid the system from kicking on too frequently and turn on enough to condition the air when the indoor temperature reaches that higher number.

If you have a smart Wi-Fi thermostat, you can control that setting from a mobile device (via an app) and return it to your usual setting before heading home, so your central air conditioner will start cooling down the house again; or you can utilize vacation/away scheduling if the thermostat has that feature and have it preset to return to your usual setting before you get home (and arrive at a relatively cooler house).

Avoid rush hour brownouts

If you’re in the habit of turning off the AC when you’re at work, remember that when everyone is coming home from work at 5 or 6 o’clock, they are doing the same thing as you—turning down the temperature in the house to have the air conditioner kick on. In addition to the burden this puts on your HVAC system, this communal activity puts a strain on the power grid, resulting in lower power or brown outs.

Lower power availability or brownouts make AC units inefficient as they struggle to condition the space. Long story short, units are most efficient when they are tasked with maintaining a constant temperature throughout the day.

Other ways to keep your indoor air nicely conditioned and energy bills in line

• Installing an attic fan takes a significant amount of pressure off your central air conditioning system (and helps maintain temperature control in the winter, too).
• During the hottest parts of the day (or when you are away), keep shades down to keep block direct sunlight and keep rooms a bit cooler.
• Unplug electric appliances that won’t be in use why you are away to reduce their electrical and heat output (yes, they draw electricity when plugged in but not in use).
• Be sure to conduct your routine spring and fall HVAC maintenance to ensure your system (both air conditioning and heating units) are working at their best.

If you return from vacation and discover your air conditioning is not working at its usual level when you return your setting to the usual temperature, contact Bloomfield Cooling, Heating & Electric at 973-237-0505 for a troubleshooting service call.