Window unit vs central air
 

We're trying figure out which would be cheaper. In the past we've run a small unit in our bedroom to keep cool at night, the central is off at this point. Saved us from having to crank the central a little higher. The unit was a little to big so it may not be a good comparison. That unit is now upstairs since our sister is living up there, no central air to the second floor. A small a/c window unit at Walmart runs $89-ish. I would compare kilowatts and all that but our central a/c is so old without hooking up an actual meter probably wouldn't be able to calculate correctly. We usually plan to keep the central off till July unless it hits 100. Anybody with a little insight.. we have a few weeks before we'll think about buying one.

It depends on how many people are running around your house at any given time of day. If you're single and live alone, I'd think the window unit would be cheaper to run. You only need the room that you're in to be cool. At night, you can only sleep in one place. No sense in cooling the whole house, especially when heat rises to higher floors.

Make sure you choose the right size unit for the size of the room. The new compressors are super efficient and cheap to run. Do compare the yellow sticker efficiency ratings on various units. Spending a few more $$ for a higher quality unit can save more electricity.

In the long run you should check pricing on replacing your old central A/C unit with a newer, more efficient one. The efficiency is remarkable improved over even units sold 5 years ago. I don't see your location, but if humidity isn't a big problem where you live you could be very comfortable running the central unit (a new one) at 78-80 degrees for the first floor while adding spot cooling with ceiling or box fans.

I keep my house at 70 :(

To use, thats comfortable ... well ... 68-72

We thought about shutting off the AC and use attic fan in early evenings then run window unit in bedroom just to be able to sleep

I would like some ratings or tests results as well.

Thing is ... going out and spending $100-$200 on a window unit ... well thats 1 month of electricity at 68 degrees :)

If I lower my electric bill by 25% by using a window unit it would take 4 months to pay for it PLUS our comfort level at home would suffer.

So .... I"m wondering is if the best way is for someone to GIVE you a window unit to actually see anysavings

Well, a window unit is definitely a durable good, you should be able to keep it for years. Assuming you save $100 a year with it, and paid $200 for it, over 10 years your in the black $800, even though that first summer you bit it.