Presenting whole life cost data

Whole life cost analysis involves manipulating a mass of data which can be presented in many ways. Presentation is about finding the simplest display of that summarises the data to meet the requirements of the user.

The data problem

For even the simplest whole life cost assessment a large amount of data is generated. Models of complete buildings on spreadsheets may run into hundreds of rows and columns.

The minimum data required to generate a whole life cost plan falls into 2 categories:

• model data - period of analysis, discount rate; and
• component data - for each component: expected service life, installation and replacement costs, maintenance requirements, frequency of action, and cost.

More sophisticated models may include a variety of positive or negative costs depending on the analysis, such as energy costs, income, tax costs or benefits, other charges or grants, etc. To keep the analysis simple these additional cost data are ignored in the following examples.

Component option appraisal

A common whole life cost assessment is to compare the long term costs between two or more alternative component options.

Presentation option 1

The simplest presentation is to tabulate the sum of the capital and whole life costs. The period of analysis and the discount rate used should always be made clear.

Component B offers the better value whole life cost but the presentation does not reveal anything about the balance between capital costs and life cycle costs.

Presentation option 2

By extending the table a little to include capital costs and expected service lives, a more rounded picture of cost and performance can be gained.

A graphic presentation gives a clear visual impression of the relationships between capital, throughout life and total whole life costs.