The gasoline example for the excavator could also be considered as a consumable resource with fixed use, since its cost completely depends on the amount used, expressed in gallons, to finish a certain activity. A typical example is the cost per unit for materials, such as bricks needed to build a wall, which is equal to € 100 per pallet, regardless how much time it takes to build that wall. It is an indication that the quantity of the resource used by an activity is independent from its duration. To that purpose, the assignment of a consumable resource to an activity can be done in two alternative ways:įixed use: the unit for the cost/unit calculation of a consumable resource is anything but a time dimension. However, there are examples where consumable resource use is expressed as a time dimension. Consequently, the costs per unit are monetary rates typically not calculated per hour but expressed in other units (per weight, per length, per pallet, etc.).
Renewable resources: the costs per unit are cost rates calculated per time unit (hours, days, weeks, etc.) and per resource unit and hence are based on the total work content (= activity duration x resource demand) of the activity.Ĭonsumable resources: normally, the use of consumable resources by project activities is expressed in units that are typically different from time units. Working with 3 excavators in parallel to finish the activity makes the total per use cost equal to € 3000. The excavator itself, on the contrary, is a renewable resource and has a per use cost of € 1000. As an example, the cost per use for a consumable resource like gallons of gasoline needed to feed excavators necessary during a construction project is € 250 per delivery, regardless of the amount of gallons brought per delivery per truck (obviously, this is cost of delivery and not the cost for the gasoline itself, which will be measured by the cost per unit discussed hereafter). its resource requirement and not its total work content). The per use cost for a renewable resource, however, depends on the resource demand of the activity (i.e. The per use cost for a consumable resource is applied only once from the moment the resource is used. The cost per use is the cost for the use of a resource that can be considered as a one-time cost incurred every time the resource is used by the activity.