# Most efficient way to use a/c???



## vitauta (Jul 11, 2012)

with this this oppressively hot and extensive heat wave, i've had to run my a/c much more than usual.  i've asked around about what is the most economical way to run the a/c, continuously or off-and-on.  nobody seems to know for sure, but lots of conflicting opinions.  i have been trying to limit my central a/c use by turning it on only for short periods, with auxiliary use of a fan.  but i worry that i may be actually defeating my purpose (saving money) with the unit turning on and off as i have been using it.  does anyone have reliable information on this topic, or a link?  what an obscene summer!!!!


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## Andy M. (Jul 11, 2012)

I recommend setting the temperature and letting the AC work to maintain that temperature.  It's really no different from heating your home in the winter.

If you have a two story home with bedrooms in the upper level, you may find the top floor is always hotter.  Close the vents on the lower floor where the thermostat is and open the vents on the second floor rooms so it will cool more evenly.  Also, you can leave the fan running all the time to even out the temperatures on different levels.

If you use a floor or table fan to circulate air in the room you're in, you can be comfortably cool at a higher temperature.  Running a fan is a LOT less costly than running AC.


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## Uncle Bob (Jul 11, 2012)

*All summers are obscene here....We set them on 75* and let er rip! ~~ Some days they run a lot... other days (rainy) not so much. It balances out. YMMV *


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## Barbara L (Jul 11, 2012)

I agree with both of the above. Set it and leave it alone. Using fans (especially ceiling fans) can help distribute the air and may help make the a/c work more efficiently.


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## Steve Kroll (Jul 11, 2012)

Good advice above. We just set it for 75 during the day and 72 at night. I let the thermostat do the work. And if it gets too hot upstairs I go to the basement and sleep on the couch. It's comfortable and cool down there.

Another thing that helps is to draw all the blinds during the day, so the sun isn't beating in through the windows. That one thing seems to make a huge difference in our house.


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## Zhizara (Jul 11, 2012)

vitauta said:


> with this this oppressively hot and extensive heat wave, i've had to run my a/c much more than usual.  i've asked around about what is the most economical way to run the a/c, continuously or off-and-on.  nobody seems to know for sure, but lots of conflicting opinions.  i have been trying to limit my central a/c use by turning it on only for short periods, with auxiliary use of a fan.  but i worry that i may be actually defeating my purpose (saving money) with the unit turning on and off as i have been using it.  does anyone have reliable information on this topic, or a link?  what an obscene summer!!!!



I think it would depend on your particular a/c.  Mine doesn't have a thermostat you can set, just a dial for low to high cooling.  

Even on the lowest setting, it will run for 6 minutes, then off for only 3 minutes.  

I finally settled on running it at a colder setting for as many minutes as it takes to get the edge off, then turning it off for as long as I feel comfortable.  My electric bill hasn't been very high at all.


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## Kylie1969 (Jul 11, 2012)

We have 2 air conditioning systems 

One is throughout the whole house, it is evaporative, where you have to leave some windows open slightly. This one uses water. This one is by far the most cost efficient one.

The other one is a split reverse system on the wall...it is refrigerated and also is a heater...that one ends up costing more since it is all electricity

We tend to use the wall air con on the humid days as evaporative is hopeless on those muggy days, but it is perfect for dry heat


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## Barbara L (Jul 11, 2012)

The original post mentions central air which, from everything I have heard (and through personal experience) works best if set at a certain temperature and left on. When you find a setting that works well for you, you will stay cool without having to freeze and boil alternately.


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## Greg Who Cooks (Jul 11, 2012)

I set my AC for the warmest temperature I am comfortable with and leave it there. I also set the fan to stay on rather than cycle with the refrigeration or otherwise the air gets stuffy and clammy.

If the air gets comfortable outside at night, switch to fans as soon as outside air feels sufficiently comfortable. Depending on floor plan and room occupancy it may help to close up the house except for two windows (across the house to provide cross ventilation) and set a fan in one window. I like to have an exhaust fan in a room other than bedroom, then leave BR window open to get outside cool air without noise of fan.

Close up the house in the morning as soon as outside temperature equals inside temperature. I can usually get a few/several hours of fan-only comfort before the temperature becomes uncomfortable and I have to turn on AC.

Wear light clothing if it will help you feel comfortable at a higher temperature. If that's no clothing then close the front blinds!


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## Cerise (Jul 11, 2012)

I have central air & heat, but wondered if these portable a/c work - just to cool down one room.  I've seen them advertised on the shopping channels.

EdgeStar Extreme Cool 12,000 BTU Portable Air Conditioner with Silver Ion Filter - AP12001S#

If I remember, the last place had a digital timer, so you don't have to run it when you're not at home, or have it shut off or turn on at a certain time.

Probably can't hurt to clean the vents, ducts & change or clean the filters regularly.

AC Duct Cleaning | eHow.com


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## CWS4322 (Jul 11, 2012)

I have one of those portable room a/c units at the farm. You do need to empty them almost every 24 hours. Fortunately, the unit shuts off when the tank is full. 

Because of TOU electricity rates, the central A/C gets turned on only during the lowest rate times--7 p.m. to 7 a.m. Running the A/C during the most expensive rate period would up the cost of running it by 66%. I try to turn it on only when the house is 28C (~82F) or warmer. During the day, the windows are closed and covered. I try to restrict the amount of cooking and the number of times the dogs go in and out, and out and in. Fortunately, we have had nighttime temperatures of about 50-52F for the past couple of nights, so windows open at night, closed during the day. It promises to heat up again tomorrow through Sunday...and with that, the humidity arrives and the nighttime temps won't be as cool.

I so hate TOU electricity rates.


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## Four String Chef (Jul 12, 2012)

The wet towel trick can cool down an 8x10 room by 7 or 8 degrees.


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## bakechef (Jul 12, 2012)

There are a lot of variables.  I live in a townhouse and it is much easier to cool than a freestanding house.  With our old system (27 years old) we would have to set one temperature and let it stay at that for 24 hours, trying to recover even just 5 degrees took hours of it running constantly.  The new system, we have it set for 80 degrees when we are not here, 74 in the evening, and 71 at night, and it cycles on and off.  It is a much better system, that is a little larger (the house has more finished square footage that it did when it was built), and recovers quickly.  

Luckily electric rates in my state aren't terrible, so it isn't extremely costly to stay comfortable.


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## Alix (Jul 12, 2012)

Four String Chef said:


> The wet towel trick can cool down an 8x10 room by 7 or 8 degrees.



What is that?


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## vitauta (Jul 12, 2012)

to what is the wet towel applied?


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## Andy M. (Jul 12, 2012)

The wet towel is probably attached to a fan in the room.


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## Four String Chef (Jul 12, 2012)

The evaporation rate of water is fairly low there for keeping the air coming off the towel cool. Place a wet towel in front of/on a box fan or ac unit. You're basically making a radiator.


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## Alix (Jul 12, 2012)

Ah I see. Thanks for the clarification. I just fill up a spray bottle and spray it at the fan occasionally. We have both ceiling fans and an oscillating fan.


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## CWS4322 (Jul 12, 2012)

Another trick is to fill a shallow pan (roaster) with ice and place in front of the fan. I used to do that for my Newfoundland--I'd place box fan on the floor (inside an x-pen so the dogs couldn't knock if over) and place a large tray of ice in front of the fan. It helped before A/C (of course, this was also b/4 TOU electricity rates--I'm back to the tricks I used before A/C to keep cool during the day).


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## Greg Who Cooks (Jul 12, 2012)

Four String Chef said:


> The evaporation rate of water is fairly low there for keeping the air coming off the towel cool. Place a wet towel in front of/on a box fan or ac unit. You're basically making a radiator.


Actually you're making an evaporative cooler. It takes heat energy to evaporate water. In other words when water evaporates it sucks up a certain amount of heat, which turns the liquid water into water vapor. Evaporative cooling takes advantage of this, in effect cooling the air in exchange for increasing its humidity.


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## Four String Chef (Jul 12, 2012)

Technicalities of a basic principle. You're right.


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## Kylie1969 (Jul 13, 2012)

Greg Who Cooks said:


> Close up the house in the morning as soon as outside temperature equals inside temperature. I can usually get a few/several hours of fan-only comfort before the temperature becomes uncomfortable and I have to turn on AC.
> 
> Wear light clothing if it will help you feel comfortable at a higher temperature. If that's no clothing then close the front blinds!



We do that too Greg...close up the house very early in the morning and it is surprising how long you can go before the house warms up...saves having the air con on all day for sure!

Good tip on closing the blinds if you opt for the "no clothing"


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## CWS4322 (Jul 13, 2012)

Greg Who Cooks said:


> Actually you're making an evaporative cooler. It takes heat energy to evaporate water. In other words when water evaporates it sucks up a certain amount of heat, which turns the liquid water into water vapor. Evaporative cooling takes advantage of this, in effect cooling the air in exchange for increasing its humidity.


Isn't this what swamp coolers do? (I think that is what the equivalent of an A/C unit in AZ is called...)


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## Greg Who Cooks (Jul 13, 2012)

Yes, I was describing swamp coolers. They utilize the principle "heat of vaporization" in that it takes heat to evaporate a liquid into a gas, and that heat subtracts from the surroundings in effect lowering the temperature. Swamp coolers work best in low humidity climates.

It's the same effect that if you wipe your face with a damp towel. The water evaporates and leaves you feeling cooler because the evaporation takes heat away with it. It takes heat to change water liquid into water vapor. Less heat = lower temperature.


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## buckytom (Jul 14, 2012)

*n*

where's everybody getting all of that ice?

i'll bet it takes more energy to make ice then to run an a.c. unit.


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## Andy M. (Jul 14, 2012)

The first hijack was a wet towel in front of a fan, which takes no energy at all.  Then we slipped into ice (or slipped on ice).

However, the original question is still about running AC efficiently.


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## PrincessFiona60 (Jul 14, 2012)

I turn mine to 66° and let it go all day until bedtime.  The extra it costs in electricity is nothing compared to the comfort I get from it.  I do have it in a window that is on the cool side of the apartment and it's in the room we use the most.  I use a fan in the hallway to pull cool air into the office, bathroom and bedroom.


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## Bolledeig (Jul 14, 2012)

66°?! How are you not freezing to death?!


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## PrincessFiona60 (Jul 14, 2012)

I run hot naturally...


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## Kylie1969 (Jul 14, 2012)

Put the cooling on to really high and then have the comfort of sleeping with the quilt on  thats what we do


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## PrincessFiona60 (Jul 14, 2012)

I'm happiest at 40°F...


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## Kylie1969 (Jul 14, 2012)

Me too Fi 

That would be 4.4 degrees celsius here


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## Bolledeig (Jul 14, 2012)

Holy moly!
I keep the house at 78 in the day and 75 during the night, and we sleep with goose down comforters. I have also banned fans.
My husband sweats all day long tho, but men have no say


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## PrincessFiona60 (Jul 14, 2012)

If Shrek gets cold, he just puts more clothes on.  We are both from cold weather states and the heat is tough on us.


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## bakechef (Jul 14, 2012)

78 when we aren't home, 74 in the evening and 71 to sleep, I'd keep it colder but my other half would freeze to death.  When I was single, you could have left the fridge door open and the food would have stayed fresh, lol!


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## Four String Chef (Jul 14, 2012)

PrincessFiona60 said:
			
		

> I'm happiest at 40°F...



40 degrees and rainy for myself. Overcoats and coffee all day.


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## Greg Who Cooks (Jul 14, 2012)

One thing about cold vs. heat, for cold you can always heap on more clothing; for heat once you've taken everything off you've reached a limit where you can't get any cooler.


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## Kylie1969 (Jul 14, 2012)

That is exactly how I feel Greg!

Another reason to the list of many as to why I hate Summer


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## PrincessFiona60 (Jul 14, 2012)

I miss wearing sweaters and my comfy, fuzzy clothes.


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## Four String Chef (Jul 15, 2012)

Greg Who Cooks said:
			
		

> One thing about cold vs. heat, for cold you can always heap on more clothing; for heat once you've taken everything off you've reached a limit where you can't get any cooler.



You can only get so naked. And the police look down on it too, I hear.


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## taxlady (Jul 15, 2012)

Greg Who Cooks said:


> One thing about cold vs. heat, for cold you can always heap on more clothing; for heat once you've taken everything off you've reached a limit where you can't get any cooler.


That's what my friend from Texas used to tell people, when they were surprised that she liked the Canadian climate.


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## Greg Who Cooks (Jul 15, 2012)

Four String Chef said:


> You can only get so naked. And the police look down on it too, I hear.


Thus my caution to close the front window curtains.



taxlady said:


> That's what my friend from Texas used to tell  people, when they were surprised that she liked the Canadian  climate.


Just for the record, I'm a California boy and I'm not suited for colder or hotter climates. No Chicago and no Phoenix in my future...

No matter what anybody can say about Southern California, it has one of the greatest climates in the nation, in terms of year round moderate weather and temperatures, and lack of hurricanes. Although we do have earthquakes....


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## Andy M. (Jul 15, 2012)

Greg Who Cooks said:


> ...Although we do have earthquakes....




...and smog.

Everybody has an attachment to where they live (or lived) and it's the best for them.

While you like the year-round moderate temps, I enjoy the changes of seasons.  To each his own.


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## babetoo (Jul 15, 2012)

Kylie1969 said:


> Put the cooling on to really high and then have the comfort of sleeping with the quilt on  thats what we do



me too! i do set the a.c. to 75. that is about right for me.


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## Four String Chef (Jul 16, 2012)

Greg Who Cooks said:
			
		

> Thus my caution to close the front window curtains.
> 
> Just for the record, I'm a California boy and I'm not suited for colder or hotter climates. No Chicago and no Phoenix in my future...
> 
> No matter what anybody can say about Southern California, it has one of the greatest climates in the nation, in terms of year round moderate weather and temperatures, and lack of hurricanes. Although we do have earthquakes....



Did the earthquake trip when I visited me mother in LA as she was attending the "baskin robbin cake school". (a must do after signing the contract with corporate). I think I was 8 or so. Earthquakes suck; you can't hide from them. I've been in a few tornados and let me tell you, give me 5 or a 6 on the the scale any day above a tornado. It's all terrifying, though.


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