On vs. Auto: One of These Thermostat Settings Costs You More Money

September 09, 2014

Have you ever looked at your thermostat and thought, “What the heck is the difference between ON and AUTO? Does it really make a difference?”

In fact, it does make a difference! Keeping your thermostat to ON can actually cost you more money. We’ll explain why in this article.

The difference between ON and AUTO

ON and AUTO describe how your AC’s blower works. The blower is the part that pulls in and distributes air throughout your home.

The AUTO setting is what most people use. It means your blower automatically works ONLY when the air is being cooled. When the thermostat senses that your home has reached your set temperature setting, the system, including the blower, shuts off. This is the most energy efficient option.

ON means, you guessed it, the blower is always on, even if the air isn’t being cooled. There are pros and cons for using the ON setting:


  • More even air distribution in your home
  • Less starting and stopping of the blower, meaning it will last longer
  • Helps your air filter or whole house air cleaner catch airborne particles more often, leaving you with cleaner air


  • Increases your electric bill— That blower is constantly using electricity!
  • Increased humidity level in your air— There’s lots of moisture on the cold indoor coil after the AC stops running. Having the blower constantly running will distribute that moisture throughout your home.
  • Filter needs changing more frequently— A dirty air filter can cause damage to your AC. So if you leave the blower running and don’t change that filter, prepare for problems.

How to get the best of both worlds

Wouldn’t it be great if you could get the best of both ON and AUTO (increased air distribution and energy efficiency)?

Well, there is a way. Next time you are considering buying an central AC system, look for what’s called a “two-stage” air conditioning system.

Without getting into too much detail, a two-stage unit has a special compressor that allows it to run at lower speeds in milder weather (unlike a single-stage system, which can only run at one speed: full blast).

This let’s the blower run more often while blowing cold air, but at a reduced cost. This gives you some great benefits including:

  • Better circulated air in your home
  • Better dehumidification
  • Lower energy bills because there’s less starting and stopping

If you are looking to replace your system soon, talk to us. We can explain more about 2- stage cooling systems

Advanced Air has been serving Fort Myers and Naples, Florida, and the surrounding areas for over 25 years.