Fig. 3. Payback period as a function of fuel price escalation, as computed by a folk model and an expert model

SOURCE: Kempton and Montgomery (1982)

calculations made by the folk model: it approximates the ways most individuals calculate, if they calculate at all.

More fundamentally, there is a problem with the very notion of users as investors. People do not see their purchases of energy and energy-using equipment only as investments; they have meanings unrelated to the cost of fuel. Car purchasers, for example, do not look solely at fuel efficiency. They are also concerned with performance, safety, styling, status considerations, and other factors. To take another example, decisions about home improvements can have major implications for household energy use. The homeowner may view these decisions as economic investments, in the sense that home improvements may have a continuing benefit by reducing operating costs, but they also have implications that do not easily translate into return on investment. They may increase comfort, provide more space or light, or improve the appearance of the home. Thus, when a homeowner considers reinsulating or replacing a working furnace, that choice is competing against unlike alternatives—another bathroom, a picture window,