On 8/10/2012 10:59 AM, Han wrote:
"HeyBub" wrote in
m:

bob haller wrote:

but energy efficency wise your far better off with a central AC. more
comfy, much more efficent, no window tied up with a AC, unusable for
anything else, no winter air leaks, even if you seal the unit great
the cold from outdoors will be conducted indoors.

I disagree.

Consider a typical usage pattern:

A. 6:00 am - 7:30 am | Usually no need for a/c.
B. 7:30 am - 6:00 pm | a/c off while everybody's at work
C. 6:00 pm -11:00 pm | a/c on
D. 11:00 pm - 6:00 am | Need for a/c while sleeping

If you use only central air, it will be on 12 hours a day (C + D). If
you have a window unit in the bedroom, the central air will be running
only five hours a day (C) and the window unit running seven (D).

The cost difference is between the central air and the window unit for
seven hours a day. Even if the window unit is not particularily
efficient, it will still cost less than cooling the whole house for
those seven hours.

There are obvious exceptions: For example, four bedrooms each with its
own window unit may be more expensive than the central unit. But the
main point remains: why cool the whole house when only part is
occupied?

You are forgetting important advantages of not having window units.
Firstly, the rooms are much lighter, less need for lighting. Secondly,
if it cools a little outside, it is very easy to open the windows and get
natural cooling. Try that with window units. Lastly, it is generally
more comfortable and efficient for 1 whole house A/C unit than 4 or more
window units. Of course, that presumes adequate insultion of the home.

I had two through the wall units in my last house; they came with the
place and I'd never seen any before. At the time I bought, the house
didn't have central air, and those units were really handy. Even after I
installed CAC, I got a lot of use out of the wall units. The CAC didn't
work perfectly in the rowhouse (it was good and cold in the basement,
adequate on the 1st floor and better than nothing on the 2nd). The wall
units were really helpful at helping cool off the bedroom, and also let
me keep the rest of the house set to a warmer temp. (My real estate
agent was worried a potential buyer might want me to remove the wall
units, but fortunately that wasn't a problem).

I liked being able to open the window if I wanted, although to be honest
I didn't very often because they were the old metal casements and
difficult to control... which probably explains why there were no window
units when I bought the house.