Optimum setting for a Dual Zone A/C unit (how much, house)

[szvegas]

After a HUGE Electric bill last month, I am hoping to get some advice on what to set the thermostat on. I have a 2 story house and the family room is open to the second floor. All the bedrooms are upstairs. We like to keep the house around 74. Should the downstairs be a few degrees cooler then the upstairs or vice versa? I have gone to different websites and I keep on getting conflicting info. Thanks for any help.

[10scoachrick]

Originally Posted by szvegas

After a HUGE Electric bill last month, I am hoping to get some advice on what to set the thermostat on. I have a 2 story house and the family room is open to the second floor. All the bedrooms are upstairs. We like to keep the house around 74. Should the downstairs be a few degrees cooler then the upstairs or vice versa? I have gone to different websites and I keep on getting conflicting info. Thanks for any help.

Well now...we have a well insulated 6 year-old Drees home that is shaded in the morning and late afternoon. I'm afraid we would go broke trying to maintain a 74 degree temp during the day(actually pretty tough at night lately). Fortunately, our master bedroom is on the first floor and we can leave the thermostat fairly high upstairs for much of the day. I actually find 74 at night to be cooler than I need. DW is already under the covers @ 76 .

Depending on how you use ceiling fans, cooling the upstairs more than downstairs will displace the warm air and move it from the first floor UP.(sometimes described as 'heat rises'). Eventually, all of the house will be cooled but that's not what you need at night(with your beds upstairs). It's tough with the open family room design. You almost need to concentrate on cooling just the bedrooms at night(challenging, depending on where your returns are located).

If someone is at home throughout the day(as we often are), you need to choose your battles. I 'suffer' a bit in my upstairs 'wreck' room--the only upstairs room used throughout each day--and leave the fans running with the 'stat set on 78-80. We keep the downstairs 76-78 during the day and that seems to be the 'sweetspot' for us AND the HVAC. We bump the 'stat to 80 if we're going to be gone a while and it cools down quickly when we reset it upon our return.

In other words, "IT"S HOT" and you might find 76-78 'fairly' comfy and MUCH easier on the wallet! Good luck!

Disclaimer: All of this presumes the HVAC system to be in good working order. If the 'drop' is not up to specs, the system may simply have to run much too long to achieve the desired temp--resulting in much higher energy use and cost.

[AustinTraveler]

You're keeping the temperature way too low. Wear shorts and tank tops and keep your a/c at 80 during the day. Make sure you close the blinds if the sun is streaming in. Also, solar screens make a huge difference, especially on the south side of your house, or if you want bedrooms to be darker.

At night we turn the a/c down to 77. The ceiling fans go 24/7 in every room in the house. Upstairs we keep at 80 all the time unless we have guests. I realize your bedrooms are upstairs but are you hanging out there during the day? No need to have the a/c set to 74 during the day.

You get used to the higher temperature. I would FREEZE to death if my house was 74 all the time.

[hoffdano]

My recs:

1. 74 is unusually cool for a daytime temperature. I suggest you make an attempt to get comfortable with 76 to 78 during the day. Our daytime temperature is set to 77 and all members of my family think it is perfectly comfortable.

2. If you do not have programmable thermostats, buy them for each unit and install them or have them installed. If you are not home much during the day - let the temperature go up to 78-80 while you are out of the house and let the thermostat change it for you when you are home.

3. get your AC units checked out for proper functioning.

[RevMen]

For a big a house, a programmable thermostat can pay for itself in a few months.

There are relatively inexpensive thermostats now that allow inputs for motion/occupancy sensors. These are especially useful for multi-zone systems where it's harder to set a thermostat schedule because you're not sure what part of the house you'll be in.

I use the BAYweb thermostat, which is controllable and programmable via the internet (or a local computer on the network). It has inputs for occupancy sensors and remote temperature sensors, though I'm not using either just yet. BAYweb

[la60336]

I am able to track on a daily basis how much energy is being used, and how much I am being charged. It seems to be about $1 less/day to actually turn the air off while I am gone, and turn it on to 78 degrees when I get back home. The temperature of my house is about 84-85 degrees when I get home. I am mot sure it this will have any negative effects...I have been experimenting with this for about 2 weeks now.

[llkltk]

Mine is set to 77 upstairs and down. The bill isn't too bad. 74 is silly. You really don't need it that cold. Get some ceiling fans.

[mark311]

We keep both our upstairs and downstairs at 78 when we're home and 80 when we're not home.

[szvegas]

Originally Posted by 10scoachrick

Well now...we have a well insulated 6 year-old Drees home that is shaded in the morning and late afternoon. I'm afraid we would go broke trying to maintain a 74 degree temp during the day(actually pretty tough at night lately). Fortunately, our master bedroom is on the first floor and we can leave the thermostat fairly high upstairs for much of the day. I actually find 74 at night to be cooler than I need. DW is already under the covers @ 76 .

Depending on how you use ceiling fans, cooling the upstairs more than downstairs will displace the warm air and move it from the first floor UP.(sometimes described as 'heat rises'). Eventually, all of the house will be cooled but that's not what you need at night(with your beds upstairs). It's tough with the open family room design. You almost need to concentrate on cooling just the bedrooms at night(challenging, depending on where your returns are located).

If someone is at home throughout the day(as we often are), you need to choose your battles. I 'suffer' a bit in my upstairs 'wreck' room--the only upstairs room used throughout each day--and leave the fans running with the 'stat set on 78-80. We keep the downstairs 76-78 during the day and that seems to be the 'sweetspot' for us AND the HVAC. We bump the 'stat to 80 if we're going to be gone a while and it cools down quickly when we reset it upon our return.

In other words, "IT"S HOT" and you might find 76-78 'fairly' comfy and MUCH easier on the wallet! Good luck!

Disclaimer: All of this presumes the HVAC system to be in good working order. If the 'drop' is not up to specs, the system may simply have to run much too long to achieve the desired temp--resulting in much higher energy use and cost.

Thanks for the info. I agree that 74 is low for Texans, but with a husband from Chicago we feel comfortable in the cooler temperature. I think that because we have a lot of windows and a 2500 sq ft home that has a living room open to the second floor it is challenging in the summer. On the flip side our winters are cheap. It seems that most replies keep the a/c the same upstairs and down, but this goes against what our a/c guy told us. I am just trying to get some advice on whether or not to set the thermostats a few degrees different, or completely shut off the downstairs at night. I appreciate your response.

[motherofthree]

We have the same kind of house as you - all bedrooms upstairs with an 1st floor family room open to 2nd floor (we have 3000 sq ft). We moved from NW Indiana 3 years ago, and like you, wanted to keep the a/c between 73 - 75. We were fortunate that that was the summer of '07 and outside temps were not that bad. Well summer of '08 changed all that and we have now acclimated to TX weather.

I have experimented a lot with the a/c temp. We now keep downstairs during the day at 77. I'll kick it down to 76 if it's more humid outside. We turn off the downstairs at 10 pm and turn it back on at 6 am. It doesn't take long to cool it off because it doesn't warm up very much.

The upstairs we keep at 80 during the day - hard for me when doing chores but 78 was so expensive and the a/c ran all the time. We drop it to 78 at night and have good ceiling fans that make a world of difference when sleeping at that temp.