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-   -   Better to leave A/C on all day? (http://www.diychatroom.com/f2/better-leave-c-all-day-111379/)

This Old Spouse 07-20-2011 10:40 AM

Better to leave A/C on all day?
 
I'm wondering if it's better to leave the A/C on all day or turn it off and have it try to catch up in mid-afternoon when it's hottest? :huh:

Mr Chips 07-20-2011 10:53 AM

I looked into this same thing a few years ago and everything I read says it's better to shut off and turn back on when you need it. I think the theroy was that A/C units are most effieicent when they run all out, rather then coming off and on in short spurts all day. I just program my thermostat to come on about 30 minutes before we usually get home, and I have it go off late at night, then come back on for a couple hours in the morning. My electric bills seem to be much lower than some of the ones I hear my neighbors crying bout

gregzoll 07-20-2011 10:56 AM

I have mine set at 76 when away, 72 when home, and 70 at bed time. EPA guidelines state 76-78 when home, and 81 when away. Those do not work everywhere, so you have to adjust according to where you live.

Mr Chips 07-20-2011 11:05 AM

Quote:

Originally Posted by gregzoll (Post 689981)
I have mine set at 76 when away, 72 when home, and 70 at bed time. EPA guidelines state 76-78 when home, and 81 when away. Those do not work everywhere, so you have to adjust according to where you live.

70 degrees?

You mid-west guys must have sides of beef hanging in your livingrooms:wink:

DrHicks 07-20-2011 11:15 AM

Quote:

Originally Posted by This Old Spouse (Post 689969)
I'm wondering if it's better to leave the A/C on all day or turn it off and have it try to catch up in mid-afternoon when it's hottest? :huh:

That depends on several factors.

We have a big brick house, built in 1928. All the walls are still plaster. I've super-insulated & all that junk.

We have a programmable thermostat, but I found that it's best - and most economical - to just set our thermostat at one temperature, and leave it. Winter or summer, it's the same story.

Also, we happen to have about 10 very large trees that provide a lot of shade in the summer.

Our house is 4400 square feet, and our total monthly utility bill is $110 per month (budget plan, so the same amount every month).

DrHicks 07-20-2011 11:17 AM

Quote:

Originally Posted by gregzoll (Post 689981)
I have mine set at 76 when away, 72 when home, and 70 at bed time. EPA guidelines state 76-78 when home, and 81 when away. Those do not work everywhere, so you have to adjust according to where you live.

Dang - that's gotta be quite a shock to walk in from outside these past few days!

biggles 07-20-2011 11:40 AM

electronic thermostat?
 
if it is :wink: just like in the winter ......setting it higher in the summer to maintain the unoccuppied temp 78F "LEAVE" then set "RETURN" for 70F as the sun swings on the windows during the day the unit will cycle to maintain 78F and as the RETURN time nears you coming home it will cycle up to give you 70F at that time then till SLEEP time/temp kicks in.most stats run Wake/Leave/Return/Sleep adjustments with hour and temps to,the lower the LEAVE is to the RETURN in temp setting the quicker it will recover but then it is also maintaining that temp during work hours $$$$$ :huh: take into consideration the sun banging the house hitting sills floors walls...if it is minimal your saving right there...

gregzoll 07-20-2011 02:08 PM

Quote:

Originally Posted by Mr Chips (Post 689988)
70 degrees?

You mid-west guys must have sides of beef hanging in your livingrooms:wink:

Actually not that cold, unless the humidity level in the house drops below 47%. Our basement stays around 66-68 during the Summer. Right now it is 95 with a feels like of 106.

Now, Winter time our thermostat is set at 60 for bedtime & away, 68 when home until bedtime. My electric & gas come out at about the same costs all year. Gas is on a budget pay, electric is low rates, so it evens out around $68 most of the year, $86 at the highest. Gas because it is Ameren, comes out at January around $112.

gregzoll 07-20-2011 02:09 PM

Quote:

Originally Posted by DrHicks (Post 689997)
Dang - that's gotta be quite a shock to walk in from outside these past few days!

Not really.

NitroNate 07-20-2011 02:11 PM

i've thoroughly run and tested my a/c at several thermostat settings over the last few years here in very HOT texas. it definitely helps to set the temp up a few degrees during the day when you are gone and let it catch up when you get back. there are tons of theories surrounding this and i'm sure a lot of factors that effect overall performance, but i think the main idea is that having your a/c run continuously as opposed to a lot of cycling off and on is better. plus, it's cooler in the evening when you turn it back on so it doesn't work as hard to cool. i would recommend no more than a 3-4 degrees temperature difference. i set mine to 79 and 82 which always seems to work out to about 77 - 80 actual temperature in the main area of the house (thermostat location is never perfect and you will have fluctuation).

This Old Spouse 07-20-2011 02:20 PM

Quote:

Originally Posted by Mr Chips (Post 689988)
70 degrees?

You mid-west guys must have sides of beef hanging in your livingrooms:wink:

Only in January :wink:

Tizzer 07-20-2011 04:07 PM

I set mine at around 78-79 when I leave in the a.m. and usually keep it there when getting home, though I'll turn on the ceiling fan.
If I don't turn it down to around 73 at bedtime, it won't cycle and I wake up with a wet pillow.:mad:

4just1don 07-22-2011 10:04 AM

80 is good enough for me. then I have small fan on low. I hate ceiling fans, feels like your head is in a buzz saw and always blowing down your neck.

In winter 68 is warm enough. wear a sweater if cold. Long as the nose and ears arent cold. cuts utility bills both ways.

Here if you shut ac off in day have to open windows, humidity in house is worse than temp, hard on food keeping, furniture and house. turn it on and leave alone.

WirelessG 07-22-2011 01:42 PM

Quote:

Originally Posted by Mr Chips (Post 689978)
I looked into this same thing a few years ago and everything I read says it's better to shut off and turn back on when you need it. I think the theroy was that A/C units are most effieicent when they run all out, rather then coming off and on in short spurts all day. I just program my thermostat to come on about 30 minutes before we usually get home, and I have it go off late at night, then come back on for a couple hours in the morning. My electric bills seem to be much lower than some of the ones I hear my neighbors crying bout

My understanding is that an AC unit that only runs for a short time will not run long enough to reduce the humidity. And this is why they say oversizing the units on your house is as bad as undersizing them.

Similar to you, I let my AC run up to 78 during the day and drop to 72 about an hour before I get home. My ground flooring is a stained concrete slab, which helps keep the downstairs a little cooler. I've tried running up the temp upstairs higher than 78, but it takes a long, long time to cool off.

Thurman 07-22-2011 07:55 PM

I'm glad someone threw the humidity factor in here. I have never understood how here in SW GA. we can have temps breaking 100's for days on end at this time of year, and they say the humidity is 100% at mid-day also. If it ain't raining, how can we have 100% humidity? My mind tells me that with 100% humidity I should be underwater. I have a programmable thermostat also. It's programmed to set the temp to 78 when I leave home in the a.m., then go to 76 just before I get home about 4-ish p.m. At 8 p.m. it goes to 73 to cool it down before going to bed, and it's still hot. At 11 p.m. it does go to 70 degrees until the morning setting of 78. Believe me, 70 degrees with 100% humidity is not as cool as I would like it and NO you cannot hang beef in here. My unit is serviced yearly and has had no work performed on it since new. Just another advantage (?) of living in SW GA.


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