Auto or On? The Best Setting for Your Thermostat

It’s a question we’re often asked: Should you keep your thermostat set to on and running 24/7, or opt for the intermittent cooling cycles of auto mode? Both have their fair share of pros and cons. It’s up to you to choose which is best for your home, but we’ve broken down the benefits and drawbacks to help you decide.


The fan turns on when a cooling cycle starts and turns off when it ends. The thermostat sends a signal to the system, which helps the fan know when it’s time to start running again.


The fan runs continuously, circulating air throughout your home. This air may be lukewarm between cooling cycles.


Setting your thermostat to auto: pros

Lower energy usage

The auto setting uses less energy since the fan only runs during the cooling cycle. The auto setting also keeps the fan running at the slowest speed for the least amount of time necessary. If energy-efficiency is important to you, then you’ll want to set your thermostat to auto.

Lower monthly cooling costs

Auto is the setting to choose if you’re concerned about monthly cooling costs. You’ll likely pay less than you would if you kept the fan on at all times, since you won’t be using as much energy.

More control

With the auto setting, you can determine when the fan turns on, and when it shuts off. With a programmable thermostat you can take it even further by tailoring your home’s temperature to your schedule. For example, if you’re home in the mornings, but away at work throughout the rest of the day, you can program the thermostat to automatically increase or decrease the temperature as needed.

Setting your thermostat to auto: cons

Uneven cooling

The auto setting keeps the fan running during a cooling cycle, but not a second longer. This means that when it’s done, it’s done until the next cycle. Homes that already have issues with uneven cooling and stubborn rooms that never quite cool down might benefit more from the continuously circulating air of the on setting.

Wear and tear

It takes a lot of effort for your system to turn on and off. With an auto setting, the frequent start/stop cycle can cause vital components to wear out faster. When components wear out, problems emerge— like short cycling, frequent breakdowns, and more. If you intend to keep your thermostat on auto, consider protecting your system with a start assist kit. These electrical tools attach to the condenser of your air conditioner and give it a boost of extra voltage to help it through the startup process. This helps prevent damage to the system and helps it conquer the demands of an Arizona summer.

Setting your thermostat to on: pros

Improved air circulation

When the switch is in the on position, your system’s fan will stay on and circulate air even after the system’s heating or cooling cycle is complete. This helps to continuously circulate the air in your home, which can even out the temperatures in every room.

Assists with filtration

More air circulation means better air quality. Air filtration and purification systems need air flow in order to work, and if your fan is always running then there’s always a supply of clean air. If you have certified HEPA filters in your home, setting your thermostat to on ensures that all the air in your home is filtered for allergens, microbes, and more.

Setting your thermostat to on: cons

Higher energy usage

Having the fan running continuously means higher rates of energy consumption across the board. This is especially true because most systems only have a fan that operates at one speed, without taking into account times of the day when less cooling is needed.

Higher monthly cooling costs

The fan in your air conditioner may not be big, but it can make a big impact on your monthly cooling costs if it’s running 24/7. More energy and power usage mean more money coming from your wallet. In fact, steering clear of the on setting is one of the tips we recommend for keeping your home cool and comfortable without spending a fortune every month.

Frequent filter changes

If your system’s fan is running continuously, your filters will clog up faster as a result. You’ll need to change your filters more frequently to counter this—aim for every 30 days instead of every 60 days. If you want to cut down on the amount of disposable filters you go through, consider reusable filters instead. Not only will this reduce waste, you’ll save money by reusing a filter instead of buying a new one.

The best of both worlds: variable speed air handlers

Most air conditioners have a traditional air handler, or fan, that only operates at high speed. Variable air handles are an innovative option that can operate at different speeds according to your home’s temperature at different times of the day. For example, if it’s the middle of a hot afternoon, the air handler will run on high. If it’s the middle of the night, it will likely slow down to low speeds. No matter what, the air handler is always on—but using much less energy than a traditional handler.

The benefits of a variable speed air handler include:

  • Consistent, even cooling
  • Better air quality
  • Energy efficiency
  • Quieter operation than typical air handlers
  • Less wear and tear on vital components

Along with the above benefits, your monthly energy bills are likely to decrease with a variable speed air handler. And, since components won’t wear out as quickly, you can potentially avoid costly repairs or an untimely replacement.

Thermostat questions? We’ve got the answers

From programmable models to innovative smart devices, Chas Roberts knows thermostats inside and out. After all, they’re the command centers of the air conditioners that we work on every day. Whether you’re tinkering with settings or troubleshooting a problem, trust our experts to help you find the right solution for your home. Contact us to get started.