Repair or Replace
In the previous post I talked about how vintage toasters were simply designed and well suited to repair, unlike some of their descendants. Yesterday’s New York Times ran the article Appliance Anxiety: Replace It or Fix It?. The article describes how people are more apt to repair appliances these days because of the economic downturn. The 50% rule, whereby if the cost of repairs exceeds 50% of the price of a new machine, is even being ignored. Some people need those savings now. The article talks about how expensive repairs, and especially parts can be, and points out how older machines tend to last longer. It closes with this rule of thumb that the vintage toaster aficionados would appreciate:
The best way to avoid the hassle of repair, according to numerous repairmen and Consumer Reports, is to buy the simplest possible appliance. “The more doo-dads, the more stuff you add to an appliance, the more likely it’s going to need a repair,” said Mark Kotkin of Consumer Reports National Research Center. Consumers would also be wise to recognize that the more sophisticated the equipment they buy, the more complicated — and expensive — the repairs can be.
This also brings to mind the equipment replacement problem often taught in OR courses. You have a machine, such as an automobile, with annual operating costs that increase as the machine ages. Each year you have the option to replace the machine by trading it in at some depreciated value and purchasing a new one, or you can hold on to it for another year. The objective is to determine at what points, if any, to replace the machine in order to minimize overall cost. It can be formulated as a shortest path problem, or solved directly using dynamic programming.
In a version more in line with the situation described in the Times article, the operating costs take on a more stochastic nature depending on whether or not the machine needs repair in a given year. The current economic tightening could be represented by a constraint on funds at some point(s) in time. Disposal, recycling, manufacturing costs could also be rolled in.
If you know anyone who was living in the US and relatively affluent in the 1950s and 1960s, ask them how often they bought a new car. Chances are they will tell you they did it every year. Undoubtedly some social status measures factored into the objective of that problem.
update: Cover story of Aug 2011 issue of Consumer Reports is “Repair or Replace It?”.