Use this modelling type when you want the quantity of the resource allocation to be in proportion to the work on the task by default. If the task's work increases, the quantity of the resource increases proportionally. Using this modelling type, the Quantity field is disabled, as this value is calculated from the task.
In order to use this modelling method, you must set the amount of work on tasks to which the resource is allocated. You can do this in one of the following ways:
- Right-click the task and select Properties to display the Bar and Task Properties dialog, click the Task tab, and record the amount of task work in the Task work and Work unit fields in the Effort & Modelling section.
- Define a column in the spreadsheet that displays the Task Work field and enter the value in the column.
- Select Quantity From Task in the Modelling type field.
- Select a Calculated Parameter and Balancing Parameter from the Parameters group. The calculated parameter is the information that you want Powerproject to calculate; the balancing parameter is the information that you want Powerproject to change automatically if the task duration is amended in the bar chart. Setting a balancing parameter of None creates a fixed resource allocation that does not change if the task duration changes.
- Enter the quantity of the resource that is consumed or supplied per unit of work on a task by default in the Task conversion factor field. For example, in a project to refurbish a hotel, it may take 4 litres of paint to paint each room, so the task conversion factor would be 4.
- Enter the default consumption or supply rate of the resource in the Consumption Rate field.
- Select the default rate type that you want to use (Units Per Time Unit or Time Units Per Unit) in the Rate Type field.
- Enter the default duration for which the resource works in the Duration field. Either the Quantity, Consumption Rate or Duration field is disabled, depending on the selected calculated parameter.
For example, in a project to refit a hotel, there is a Refurbish Bedrooms task. For each bedroom you need a selection of consumable resources, including litres of paint. Each room requires 4 litres of paint and they are consumed at a rate of 2 litres per day. If there is 1 bedroom to refurbish, 4 litres are consumed; if there are 10 bedrooms to refurbish, 40 litres are consumed. If the work on the task is set to 10, the Work field automatically displays 40 - that is 10 rooms multiplied by 4 litres of paint. If you enter a consumption rate of 2 litres of paint per day and choose Duration as the calculated parameter, Powerproject calculates the duration of the resource allocation to be 20 days.
If you reduce the task duration from 20 days to 10 days, the resource allocation is adjusted according to the selected balancing parameter:
- When Rate is selected, the consumption rate increases from 2 litres to 4 litres per day. As the resource allocation duration is shorter, the paint must be consumed more quickly to complete the task in less time.
- When None is selected, the resource allocation is not adjusted.