This article was originally published in the March/April 1998 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online March/April 1998

Homeowners: Who Will Demand Rightsizing?

Along with conducting detailed load calculations of 40 Sacramento homes, we asked homeowners to complete a brief survey. They told us how big their previous equipment had been, what sizing options contractors had presented, and how satisfied they were with the new equipment.

Thirty homes in the study had had existing central cooling systems replaced. Half of these homeowners reported that the new cooling system was larger than the old one. We found no significant difference between the level of oversizing in these customers' homes and that in the ten other homes in the study.

Contractors presented homeowners with a choice of sizes in almost two-thirds of the homes in the sample (see Table 1). About one-third of homeowners selected the size of their unit based on options presented by contractors, while another third selected the one that a contractor specifically recommended. However, we found that the level of oversizing was almost the same, whether the homeowner or contractor picked the size. As shown in Table 1, the portion of units that were oversized was slightly lower in cases where homeowners were presented with different sizing options. Due to the relatively small sample used in the study, however, these differences are not statistically significant.

Interviews with contractors, as well as homeowner surveys, indicate that homeowners often play a key role in determining the size of HVAC equipment installed. The engineer of a large contracting company explained that even though his company performs Manual J calculations to verify salespeople's recommendations, customers are often presented with various sizing options. After performing the load calculation, we then give consideration to the customer's preferences to determine whether to recommend a larger size unit or a slightly smaller size unit. For instance, older customers often want warmer houses. Sometimes we get a customer that wants a grossly oversized unit, thinking that bigger is better. We always explain the benefits and costs to the customer. In almost all cases we are able to convince the customer to install the properly sized unit for their home.

As another large contractor explains, We place a greater emphasis on consideration of the customer when sizing an A/C unit. [We] give the customer the option to select a larger size unit. He says the extra cost of a larger air conditioner is insignificant to many homeowners who are more interested in cooling their house down fast. For example, In a two-income household, homeowners don't leave their A/C on while they are at work. When they come home in the evening, they want a cool house fast. They want a larger A/C unit to cool the house faster. So we sell them a larger unit.

While previous reports have claimed that oversizing of equipment would affect the comfort and satisfaction of homeowners, our study did not bear this out. We found no significant difference between the level of equipment oversizing and the level of homeowner satisfaction. None of the 40 homeowners in the study indicated he or she was dissatisfied with the performance of their new cooling equipment during very hot summer periods. In fact, over two-thirds of homeowners reported being very satisfied with the performance of their new cooling systems.

Table I. Customer Options and Oversizing
  Undersized >.25 tons Within .25 tons Oversized >.25 tons
Contractor presented homeowner with no sizing options. 15 (37%) 1 (7%) 5 (33%) 9 (60%)
Sizing options presented.
Contractor recommended specific size installed. 14 (35%)
2 (14%) 5 (36%) 7 (50%)
Sizing options presented.
Customer chose specific size installed. 11 (28%)
2 (18%) 4 (36%) 5 (45%)


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