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Let me start with saying I know ceiling fans don't cool the air. My question though, is do ceiling fans help circulate the cool air from the handler in such a way that it would trigger the thermostat to less frequently turn the system on?

When we leave the house, we have the thermostat set on about 80. We live in Florida though, so the house has no issues hitting 80 and staying there basically 24 hours if we allow it; point being, the air is going to kick on throughout the day, regardless. I'm curious if ceiling fans will help it to kick on less frequently.

I guess the best option would be to set the thermostat at 82 instead of 80. But even then the question remains, do ceiling fans help lessen the time the unit is actually on?

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  • Don't set your thermostats at 82 unless you are comfortable at 80 degrees. The amount of time to re-cool the house down to say 76 or 77 will cause your ac unit to run for HOURS. Also note this is not good for your house interior and your refrigerator will work harder. See my edited Answer. – Ken Sep 2 '17 at 9:33
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A fan won't improve efficiency, rather the opposite (more circulation means more loss to the outside).

But it might improve comfort. Increased comfort can result in the occupants raising the temperature, and thus reducing cost.

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  • Precisely, and since the question as asking about efficiency, but ignoring the cost of running a fan vs. running the A/C; it stands that running the fan when no one is home is NOT efficient. Technically, neither is running an A/C when no one is home, so keeping the house at a temp that doesn't kill pets, plants, or damage the home, and installing a programmable thermostat to engage before you get home could optimize comfort and dollars out of ones pocket. – noybman Sep 1 '17 at 23:50
  • It is all about perception. Have a look at HVLS fans. Costco even recognized the value and have installed them in our area near the registers. The large fans create a column of as tall or taller than a person after it hits the ground so you get air movement and the person feels cooler even though the temperature is the same. – Damon Sep 11 '17 at 10:25
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The only thing a fan would do is it might increase the circulation or distribution of conditioned air. Also because moving air causes evaporation it would feel cooler to the skin. Lets call it chill factor, you know the weather man uses it and heat index all of the time. So if it feels cooler, you can actually set your thermostat higher by a few degrees and still feel comfortable. That would allow less run time for the compressor and energy savings.

In case you're wondering if I am a believer, I have a fan in every room in my house except for the kitchen and bathrooms.

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  • No fans in the bathrooms? Moisture? Kitchen, gases? Are you saying this because you don't want to introduce the negative pressure issue in the home and prefer to deal with (accept/live with or process) the moisture/gas issues as it is? – noybman Sep 1 '17 at 23:54
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Efficiency of your A/C unit does not change - it is just as efficient with or with out the fan.

With the Fans - you are circulating your hot air - some people use reverse air flow to pull hot air down others use forward flow - cool air upward - the difference is in where the circulation path is and of course ceiling dust.

What happens is that more of your air is being cooled in the home - so it feels a little cooler all the way around. It improves the overall cooling of the home for this reason.

Your A/C runs just the same except overall temperature is more homogeneous and so you can get away with a slightly higher thermostat temperature setting (about 2 degrees).

EDIT 9-2-2017

Don't set your thermostats at 82 unless you are comfortable at 80 degrees. The amount of time to re-cool the house down to say 76 or 77 will cause your ac unit to run for HOURS.

As for Ceiling fans they will run continuously ..how many?? One ceiling fan is like leaving your Air Handler Fan on ALL the time! More than one - multiply that.. Ceiling fans may help in that all the air is roughly at the same temp ; however they use electric and if your bottom line is $$ - that will not solve the problem, it will only aid in comfort and also preserve the AC unit a little bit.

If it boils down to dollars - you might have one of those big box Digital Thermostats - meaning it is probably a honeywell - generally the swing is .5 degrees . Get Rid of that thing and get a better t-stat - I had one of those and I can't comment without bashing it.

I had lived in O-Town 1700 Sq Feet Vaulted Ceilings through out, no trees for shade, with an East facing back Plenty of Large Open Windows and large sliding door. I used a LUX digital Thermostat and set a 2 degree swing When out of town I left it at 79 or 80 Degrees depending; in town I managed leaving it at 77 degrees with a 2 degree swing setting. The thing worked like a charm; with 2 degree swing set your temp 1 degree cooler than your 'I am ok but just a tad cooler temp might be nice'. . Your body will not notice the difference. My electric if I can remember the Highest bill I ever had I think was $140 (exceptional reason for that) .. but it usually hovered in the $100-$110 range. That was from the poorest performing AC unit the builder could install - I remember the energy tag with that arrow slider thing ...'Your Unit Annual Costs $$$$$ , all others much BETTER' - Installed by the builder!

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  • The statement that the efficiency of the A/C itself isn't changing is true, but the question he is asking is not solely on the efficiency of the A/C. With the fans the air, hot or cold, is being circulated. This is happening at a cost of running the A/C and the Fan, where the fan is "never" off. Also, as the cold and the hot air is mixing, to your point, becoming more homogeneous, it is also passing over MORE warm surfaces that it is cool (considering the walls of his house are not A/C coils) thus also artificially forcing convection, at a cost, when no one is home. – noybman Sep 1 '17 at 23:47
  • @noybman you are correct about the fans running home or not - they add to cost.The OP asked in the title about efficiency, but in his details he is alluding to costs. If OP runs the fans while OP is home - his comfort level will increase and the AC will APPEAR to perform better at keeping the house comfortable at a slightly higher thermostat setting. The walls will be cooler, the ceiling cooler..the air temp more uniform.His costs though will probably average out to the same or close to it. The worst thing he is doing is setting the T-Stat for 82 degrees; better off at 79 degrees when out. – Ken Sep 2 '17 at 9:31
  • Yea, I ran out of room... Running the fans when someone is home is definitely going to be more comfortable overall, and running them when no one is home doesn't serve any good purposes - including the time the A/C runs, in fact, because of convection, and moving a potentially stagnant portion of otherwise warm air around into cool air will warm that cool air up, and the A/C will have more reason to cool more often. – noybman Sep 2 '17 at 12:30

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