"Nehmo" wrote in message
...
If a house currently has multiple window air-conditioners, are these
significantly less efficient than central air, if the house were
retrofitted with it?

I realize the comparison is complicated, so assume all other factors
equal, and assume: the vents and their position for central air would be
adequate; about half the rooms are normally in use; nobody's concerned
about the window-view obstruction, etc.; Chicago climate; poorly
insulated house.

If Chicago is as warm as I think it is, I'd go with central if possible.
More efficient, quieter, more even temperatures in the house.

Where I live, it becomes marginal most years. Normal summer we need AC
maybe five to 8 days and maybe an additional 10 nights in just the bedroom.
That makes window units far more economical compared to running a big
system.

In warmer climates I'd never consider window units..