A/C more efficient when left on ?

[Cd]

So is it true that it takes more electricity to cool a small house ( or in my case an efficiency apartment ) than to just leave the A/C set at 72 degrees while at work ?

I bought a fan thinking that I'd save electricity, only to find out that it was drawing over 100 watts on full power. ( 62 watts on low )
This is on a typical cheap $ 12 box fan that I purchased. I think it is around 30 "
I didn't see any Energy-Star labels on the box - now I see why !!

Also, I notice that my refrigerator seems to come on at at the same time intervals regardless of whether or not it is hot or cool in my home. Why is this ?
I would think that the thing would come on more often when the outside temperature is warm.

[captainslug]

Depends on how long you are away from home. It will obviously take the most energy to keep your house at a consistent temperature from the time between noon and 4pm. If you're not home during that time leaving the system off will make a huge difference.
If you want the temperature of your home to be at comfortable levels when you get home, then you should put the unit on an outlet timer that turns it on 30 minutes to an hour before you normally get home, and turns it off right before you normally leave.

Originally Posted by Cd

Also, I notice that my refrigerator seems to come on at at the same time intervals regardless of whether or not it is hot or cool in my home. Why is this ?

Because it's heavily insulated and doesn't lose much over time as long as you leave the door closed.
A 20 degree difference in the exterior temperature of the fridge won't make a huge difference to the interval cycle because when it remains closed it only has to compensate a very small amount.

[Daox]

Wow that must be an incredibly powerful fan. My box fan (regular el-cheapo too) only pulls 13W on high! Maybe there is something wrong with yours?

I'd have to say turning the AC off is definitly more efficient. Its going to take way more power to maintain X degrees below ambient all day vs turning it off and having it come back on to maintain X degress below ambient for the few hours you are home.

If you hate comming home to a hot house, use one of those plug in timers like you would use for a block heater. Have it come on an hour or so before you get home and voala, you save energy and still come home to a cool house.

[RH77]

I think there's a system out there that either connects to a PC or is a standalone system -- anyway,

You can simply call or text your house do things like turn on the Heat or A/C (other applications are lighting control, etc.)

[SuperTrooper]

If you have central A/C you can install a programable thermostat (cheap and easy to install) and tell it to turn on the A/C about 30-60 minutes before you get home, depending on how fast it can cool your house. We use them to control the heat in the winter. While the house is empty during the day I let the temp get down to 60, then turn the system up to 68 about 30 minutes before my wife gets home.

[PaleMelanesian]

The bigger the difference between inside and outside temperature, the bigger the heat loss between the two. The ac running the whole time has to overcome the perpetual loss. If you turn it off, it only has to overcome the temperature gradient one time when it comes back on. It's almost always better to turn it off when not needed.

[Cd]

Originally Posted by Daox

Wow that must be an incredibly powerful fan. My box fan (regular el-cheapo too) only pulls 13W on high! Maybe there is something wrong with yours?

.

The fan is just your everyday boxfan.

The fan that I have is one that I bought from my job at Lowes. I have also seen the fan at other stores as well like Walmart.

The brand is 'Lasko', and since they were so cheap ( $15), I thought I'd buy two of them so that I could have one blow in air while the other exausts it.

I confirmed the reading using a KillaWatt on both fans. The settings are 61 / 80 / 97 - 104 watts on low, medium, and high power.

Its no wonder my electric bill was so high ( 200 watts running all day ! )

The fan looks like any other boxfan out there.

Just a heads up for anyone thinking of buying one of these fans to save energy. Buy one that says it is EnergyStar rated !

I guess they use junk parts that are not very efficient.

As far as the A/C question, I had been told that it would take more power to cool my apartment when I came home to a hot house rather that just leave it on all day.
It didn't seem to add up for me either. It sounds like something a power company would tell people.

And regarding the question on the 'frig : What puzzled me is that even when my apartment was really cold, the 'frig still came on every fifteen minutes.

[Axaday]

Originally Posted by Cd

As far as the A/C question, I had been told that it would take more power to cool my apartment when I came home to a hot house rather that just leave it on all day.
It didn't seem to add up for me either. It sounds like something a power company would tell people.

It is a very common myth.

And regarding the question on the 'frig : What puzzled me is that even when my apartment was really cold, the 'frig still came on every fifteen minutes.

How cold is your apartment when it is "really cold"?

[mopo3]

I did this as a project in my thermodynamics class, and the result is to always turn the AC off when you are not using it. It takes the AC a very short time to cool the air in your house, which is what makes it feel cooler to your skin.

[jamesqf]

Think about a limiting case. Suppose instead of leaving for a day, you leave for a year. (And you live someplace where it doesn't get cold in the winter.) Is it more efficient to leave your A/C on, or turn it off? Seems like the answer's obvious, no? So how about if you're only away 6 months? Or 3? One month, two weeks, etc. Same answer, no? So why would the answer change when you only leave for half a day?