BMI Mechanical Heating, Ventilation and Air Conditioning
BMI Mechanical Heating, Ventilation and Air Conditioning

Should I Turn My AC Off When I’m Not Home?

▸ March 29, 2021

Should I turn my AC off when I’m not home? What about when I’m on vacation? Should I turn off my air conditioner when I’m gone for a few days? Does turning my AC off even save me money? Or does it actually end up costing me more money in the long run?

Questions like these are extremely common. People from all walks of life are interested in knowing best-practices when it comes to their air conditioners. They want to understand how turning off their AC can impact things like energy conservation, cost-efficiency, and ideal living situations. 

While everyone has their own motivation for turning off their ACs when they leave the house, let’s quickly discuss what can save you money, keep your AC functional, and maintain a healthy living situation.

Turning AC off vs. leaving it on: What’s better?

If you want the quick and dirty version of this post, it’s usually better to keep your AC on when you leave the home or office. Yes, even if you go on a vacation for the weekend. We recommend turning the AC up a few degrees from your normal temperature (anywhere between 7 and 10 degrees).

However, this is only if you plan on being away for a few days. If you plan on being away for longer than a few days and your primary interest is to save money, then you may want to consider turning your AC off completely (just don’t forget about your furry friends).

Cons of turning off your air conditioner when you leave

There are a few things you will want to keep in mind if you do decide to turn your AC off when you leave your home or office. This primarily includes mold and bugs — two things that love humidity. 

When you turn your AC off, your space becomes more susceptible to humidity. This added humidity can lead to mold and bugs. This being said, if this is something you’re not interested in, then go back to our original advice: turn your AC up to a higher temperature when you leave. 

Other than bugs and mold, however, turning your AC off completely when you leave your house can certainly make your living situation uncomfortable when you return and could end up costing you more money in the long run. But this will definitely depend on your outdoor living environment (outdoor temperature vs. desired indoor temperature), as well as the type and size of your unit.

We typically say that a programmable thermostat (or manually decreasing/increasing the temperature) is the most beneficial option for promoting energy- and cost-efficiency, but it’s always best to consult with a licensed HVAC contractor to get advice that’s truly unique to your environment, your air conditioner, and your needs and wants.

Keep Reading: 2021 HVAC Technology Trends 

What’s the best temperature to keep your AC at?

The advice people usually give out is to remain within 15 degrees of the outside temperature, so you don’t work your AC too hard or consume too much energy. However, this is easier said than done. In most settings, 78 degrees is ideal. But what happens if you live in an extremely cold or extremely hot city? 15 degrees of 105 degrees would be 90 degrees, which isn’t exactly a relaxing indoor temperature. This would also mean that if you turned your AC up when you leave the house, you’d have a home sitting at 100 degrees (which seems a little high). Even if you turned your AC off completely when you leave for the day or for the weekend, your house would mostly likely be sitting around the same temperature.

In these more extreme circumstances, we once again recommend speaking with a licensed HVAC contractor. An HVAC company can give you more customized advice to keep your home comfortable when you’re gone (while also maintaining energy- and cost-efficiency). 

Need more advice on your home or office AC?

At BMI Mechanical, we have decades of combined experience working with businesses all over California and helping them remain comfortable in their own spaces. If you’d like to learn more about AC best practices, take a look at some of our additional resources. 


More than 55% of all building owners & managers approach their facilities reactively; giving something attention only after it breaks. U.S. Department of Energy, Federal Energy Management Program

Since 2004, BMI has provided our company with an outstanding HVAC Preventive Maintenance Program. I must say that the ‘details’ are in place at BMI. Their technicians are courteous, on time, knowledgeable and are able to take care of any problems on their first visit. Dave Cavanaugh Operations Manager UNISOURCE