Imagine entertaining guests at your home on a hot, humid day, and the central air conditioning system breaks down. Imagine that, and you easily can understand why reliability is what homeowners want most from their central air conditioning system.

A study by the Trane Home Comfort Institute, a consumer information service on heating and cooling, shows that nearly seven out of ten (69 percent) rate reliability as the most important attribute to consider when choosing a central air conditioning system. Homeowners in the study said they wanted a unit that could be counted on not to break down when it was needed most.

According to the homeowners, durability, the second most frequent response (63 percent), meant that the unit should last a long time. As one respondent put it, "It's not something I should have to purchase often. I want it to last."

The study shows that efficiency is another attribute high on homeowners' minds (59 percent). Respondents said a key question to ask concerning this feature is, "With this new system, will my utility bill be less than it was in the past?"

Completing the first tier of attributes was overall quality (53 percent). In the respondents' eyes, this meant the quality of the manufacturing, ranging from the construction of the compressor to the composition of the paint finish.

Heading up the second tier of considerations was weather resistance (37 percent). This attribute deals with how the outdoor unit is protected from the elements. Here, respondents felt cabinets with louvered full-side panels provide the most protection from rain, hail, falling leaves, dirt and children.

In homeowners' minds, affordability (36 percent) referred primarily to purchase price, since operating costs of newer units were expected to drop due to higher efficiencies. Respondents said a key question to ask is, "Is the value and comfort this system provides worth the price?"

In one of the more interesting findings, Trane Home Comfort Institute researchers found that even though respondents admitted to not knowing the inner workings of their air conditioning systems, technology was mentioned enough as a highly desirable attribute to make the list (29 percent).

Finally, when it came to sound level (23 percent), homeowners said they wanted the air conditioner to perform without making its presence known. They also felt that way about their neighbor's unit. As one respondent said, "When your neighbor's outdoor unit sits near your bedroom window, you hope he selected a quiet system."