air conditioner on 76 vs 78 degress?

Busie23

Senior member
Jan 24, 2001
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Ok, how big of a difference will it make when the bill rolls around? I have also kinda felt that it is better to leave it set at one temp all day as opposes to turning it on and off all the time? My girlfriend is always complaing about how much the bill will be when I turn it down a degree or two?

Is there any better method for cooling you house to help save a bit on the bill?
 

jcovercash

Diamond Member
Apr 24, 2001
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Well IDK how much a difference it will make by dropping it a degree or two, but I do know that if you adjust it alot it will cost you more because the system has to work even harder to reach that new temp. or something like that....
 

Gunslinger08

Lifer
Nov 18, 2001
13,234
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Originally posted by: AMDman12GHz
Well IDK how much a difference it will make by dropping it a degree or two, but I do know that if you adjust it alot it will cost you more because the system has to work even harder to reach that new temp. or something like that....

Shall I call you Captain Obvious?
 

rh71

No Lifer
Aug 28, 2001
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I'm trying to understand the reasoning behind "saving money if you left it on all day"...

You're using the air conditioner at X wattage for X kwh. I thought those were constant. Does the wattage go up if you set the A/C to a lower temperature ? How does it save you money if it's using electricity all day as opposed to 1-2 hours just to cool the place down ?
 

KenGr

Senior member
Aug 22, 2002
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Ok, this is pretty easy to estimate. There are some variables on the radiant load depending on how much shade you have, the dehumidification load, etc. But for a first order approximation, the amount of energy required is proportional to the temperature difference between inside and outside. If it averages 90 outside, the cost to bring it to 76 instead of 78 will be about 14/12 or 17% more.

Relative to jockying the temp up and down, it's more annoying than expensive. If you really turn it on and off you will get a humidity buildup that then has to be taken care of before you can effectively cool and the net result is you just won't be as comfortable.
 

Gunslinger08

Lifer
Nov 18, 2001
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It's like a thermostat. It cuts off after it reaches a certain temp. So it doesn't stay on all day.. only until it reaches 76 or 78 or whatever you set it to.
 

43st

Diamond Member
Nov 7, 2001
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Leaving it on all day is pretty stupid. Just set it to turn on 30 minutes before you get home. It's much less wasteful and you'll get the exact same results.
 

TourGuide

Golden Member
Aug 19, 2000
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We have ours set to a certain temp during the day. At night (when it is cooler) we turn the thermostat (have it programed) to turn up. This keeps the AC from running at night when it doesn't need to. It will do this if you haven't ever noticed it. In the AM, the thermostat is set to kick back to our preset temp. Works for us. We set our AC to 74 during the day, and 80 at night.
 

Gyrene

Banned
Jun 6, 2002
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Originally posted by: rh71
I'm trying to understand the reasoning behind "saving money if you left it on all day"... You're using the air conditioner at X wattage for X kwh. I thought those were constant. Does the wattage go up if you set the A/C to a lower temperature ? How does it save you money if it's using electricity all day as opposed to 1-2 hours just to cool the place down ?

The arguement there is that air conditioners, when left on all day, don't actually run all day. They cycle on and off to maintain a certain temperature and humidty level. The thermostat tells them what the target is, and what they're curently at, then the air conditioner decides when to turn on and cool/heat and when to rest.

In a Constant Air system, like most residential buildings have, you have a coil that controls temperature and a constant cfm blowing out. If you left you AC off all day and the the building temp rose to 85 degrees, and your target temp was 74 degrees, when you got home and turned the AC on to cool the house down, that coil would have to pump refrigerant through to cool the air to a temp of about 40 degrees, putting alot of strain on the unit, and raising the enegy bill. But if you left the AC on, and it kept a constant flow of 55 degree air, the unit wouldn't use as much energy and wouldn't put too much stress on the unit.

A bad comparision would be relating it to track. Take a 400 runner and a 1600 runner. The 400 runner goes all out for a short amount of time, and dies at the end. The 1600 runner paces, and when they get done, they're are usually able to still stand/talk/walk around. The 400 runner exerted a mass amount of energy in a short period of time, while the 1600 runner used a little less energy over an extended period of time. Yes I know, that comparision sucked, but I'm tired, and it's all I could think of.
 

Busie23

Senior member
Jan 24, 2001
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Originally posted by: dtyn
Originally posted by: rh71
I'm trying to understand the reasoning behind "saving money if you left it on all day"... You're using the air conditioner at X wattage for X kwh. I thought those were constant. Does the wattage go up if you set the A/C to a lower temperature ? How does it save you money if it's using electricity all day as opposed to 1-2 hours just to cool the place down ?

The arguement there is that air conditioners, when left on all day, don't actually run all day. They cycle on and off to maintain a certain temperature and humidty level. The thermostat tells them what the target is, and what they're curently at, then the air conditioner decides when to turn on and cool/heat and when to rest.

In a Constant Air system, like most residential buildings have, you have a coil that controls temperature and a constant cfm blowing out. If you left you AC off all day and the the building temp rose to 85 degrees, and your target temp was 74 degrees, when you got home and turned the AC on to cool the house down, that coil would have to pump refrigerant through to cool the air to a temp of about 40 degrees, putting alot of strain on the unit, and raising the enegy bill. But if you left the AC on, and it kept a constant flow of 55 degree air, the unit wouldn't use as much energy and wouldn't put too much stress on the unit.

A bad comparision would be relating it to track. Take a 400 runner and a 1600 runner. The 400 runner goes all out for a short amount of time, and dies at the end. The 1600 runner paces, and when they get done, they're are usually able to still stand/talk/walk around. The 400 runner exerted a mass amount of energy in a short period of time, while the 1600 runner used a little less energy over an extended period of time. Yes I know, that comparision sucked, but I'm tired, and it's all I could think of.


That was kinda how I thought of it too. I like to leave it on all day at say 78 and then when we get home turn it down to 75 or so. But the girlfriend wants to tunr it off and then turn it on when we get home. The problem is that the place heats up so much during the day that the air will run for like an hour when we get home. I'm thinking that leaving it at a set temp through the day is better than having it work overtime everyday for an hour or so, as opposed to just a few minutes throughout the whole day.

I also wish we could set it to do some of this automatically but it is a manual thermostat.
 

Tom

Lifer
Oct 9, 1999
13,293
1
76
Yea but the 400 runner recovers and is eating lunch while the 1600 runner is still running. (which means turn your air-conditioning to what you like and by your girlfriend a sweater.) :gift:
 

slag

Lifer
Dec 14, 2000
10,473
81
101
We keep our AC set to 65 degrees between April and October. We've been debating getting an electric thermostat so we can let it go to 70 or so at night and 70 or so when we are gone from home, and then an hour or so before we arrive back home from work, it would go back to 65 or so.

Its very nice.
 

TourGuide

Golden Member
Aug 19, 2000
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We keep our AC set to 65 degrees between April and October.
WHOA! THAT is really cool for an AC setting. 74 is about my minimum comfortable temp where AC is concerned. Lower than that and it starts feeling chilly. I can't imagine what 65 would feel like. I think it's probably safe to say there would be some shrinkage involved.
 

Gyrene

Banned
Jun 6, 2002
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Originally posted by: slag
We keep our AC set to 65 degrees between April and October. We've been debating getting an electric thermostat so we can let it go to 70 or so at night and 70 or so when we are gone from home, and then an hour or so before we arrive back home from work, it would go back to 65 or so. Its very nice.

Do you live in an Operating Room...we cool them to 60-65, and it's freezing. We keep the actual coil around 55 degrees. I can't fathom living in a 65 degree permenant conditioned space.
 

LordThing

Golden Member
Jun 8, 2001
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Shoot, when I had central air, I kept it at 71 all the time. My whole townhouse was electric (even ran my own washer and dryer on it) and my bills never got more than 125/month for electric. Definately worth the few bucks to me to have a cool house than to worry about setting it to higher temps or cycle it on and off. Not only does the system seem to use more energy trying to cool a hot house rather than maintain a temp (think of a oven, takes forever to heat up but only clicks on once in a while to maintain...which is more energy), but It takes forever for the damn thing to get to comfortable levels. So now I gotta sweat my butt off for the next hour or so when I just got home rather than walk into a already cool house.


 

Staples

Diamond Member
Oct 28, 2001
4,953
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Originally posted by: slag
We keep our AC set to 65 degrees between April and October. We've been debating getting an electric thermostat so we can let it go to 70 or so at night and 70 or so when we are gone from home, and then an hour or so before we arrive back home from work, it would go back to 65 or so.

You people and your crazy temps. I keep mine set at 84 during the day and 80 at night. Yes I do not like cold whether at all however my sister and mom and hell, anyabody but me complain about it being too hot in my room however a lot less than they did when I had no AC in here and it was 95-100F in here everyday.
 

Gyrene

Banned
Jun 6, 2002
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Average cooling temperature is 74 degrees. That's what you'll find in most offices, MOBs, malls, etc. IMO that's a perfect temperature. Anything up to 78 is still comfortable, anything down to 70 is comfortable. The rest of you people are psychos, and if everyone in this world were like Staples, I would be out of a job. ;)
 

Linflas

Lifer
Jan 30, 2001
15,395
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Ours is set to 72 when people are in the house and 78 during the weekdays when we are at work. It is set to start dropping to 72 about 30 minutes before I come home.
 
May 16, 2000
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I've never found the bill to increase that much from the changes in temp settings, unless you're trying to beat 100 degree heat with only one 10000btu unit, then you're gonna lose anyway so what's the point.

You can use a garden hose and spray the roof and walls and windows of your home for about 10-20 minutes 2-3 times a day and it will have a MAJOR cooling effect. Of course, in drought conditions there are usually water restrictions so this stops being an option.

I can't stand anything over 72 in the house. When it hits 75 i can no longer sleep. At 80 I do nothing but yell and complain all day. Over 85 and I turn near homicidal/suicidal. I generally keep my house around 65-70 during the days and let it cool off naturally at night, often gets to about 55-60 by morning. Unless I'm sick I don't start to feel chilled until the temp is below 55, and I'm not uncomfortable unless it drops below 40ish.
 

Rob9874

Diamond Member
Nov 7, 1999
3,314
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Originally posted by: JetsFanatic
Keep it ICE cold and don't worry about the cash

my comfort is worth way more than a couple of bucks


WORD! That's my thought exactly. I live in AZ, and my comfort level comes first. If I have to cut other areas to pay my electric bill, I will. What's nice in AZ is that you don't need heat. So we're at our peak usage right now for AC, and my bill last month was $177. But that balances out when my Nov-Feb bills are like $50-$60. I keep my AC around 70-75 degrees. It's FREEZING!