Q&A: What is "split ductless" air conditioning?

I've been reading about "split ductless" air conditioning. What is it? And is it a good alternative to central air conditioning?

Split ductless is a smart way to add air conditioning to a limited number of multiple rooms without having to open up walls to install ductwork—as you would with a central-air system—or install and remove multiple window units each year.

Split-ductless systems have an exterior condenser and an indoor evaporator unit that houses the cooling coil, a fan, and controls, to which you can add indoor blowers. (The condenser and the evaporator blowers are connected by electric wires and tubing, through which the refrigerant circulates.) Some models are designed to have two or more evaporators connected to one condenser unit. Each evaporator blower is mounted high on the interior wall of the room or area you want to cool. You control the units with a remote control. Since you might have multiple units, you can save energy by zone cooling your home, as you might do with window air conditioners. A Mitsubishi Mr. Slim evaporator blower is shown.

For our upcoming report on air conditioning, we tested three split-ductless systems with single indoor evaporator units; the systems cost $1,000 to $1,200 each. All did an excellent job cooling and were much quieter indoors and out than window air conditioners; indeed, on the low setting they were barely audible.

Split ductless is more expensive than window or portable air conditioners (professional installation is recommended) but is less expensive than central air if you are cooling only a few rooms. However, if you are looking to cool the majority of your home, a central-air-conditioning system is probably a more cost-effective choice.

Look for complete coverage of air conditioning, including window, portable, and split ductless, in the July 2009 issue of Consumer Reports (online and on newsstands in June).

Essential information: Figure out what size air conditioner you need by using our free calculator and save money while staying cool this summer