Maintenance cost estimation: application of activity-based costing as a fair estimate method
Authors: Haroun Ahmed E. 
Published: August 2015

Purpose
– The purpose of this paper is to present the use of activity-based costing (ABC) approach as an alternative option to the traditional cost accounting system. The contribution of this study is to demonstrate, through a simple example, the application of that costing system in a service (maintenance) industry, i.e. the paper intended to develop a procedure for a cost model that help in calculating any maintenance job cost, to a reasonable degree of accuracy, based on the actual activities performed.

Design/methodology/approach
– This research uses a simple example whereby hypothetical activities and cost data of maintaining an injector and a pump, of an internal combustion engine, are used, presented and analyzed based on the use of the developed procedure.

Findings
– ABC system provides more accurate cost estimates rather than the traditional “order costing” methods that uses unit-level costs which are variable in relation to change in service volume. Traditional cost methods distort the costs by applying overhead uniformly over different jobs of varied complexities and activities scope. On the other hand, ABC is a useful means to distribute the overhead costs in proportion (fairly) to the actual activities performed in a specific job and, hence, enhance the rationality of decision making, i.e. will not distort the accounting information used for cost reduction, pricing, and evaluation matters. The results obtained from the analysis showed that allocating costs to the maintained injector decreased from $83.55 to $71.95 and, finally, to $67.57 when using the workshop-wide, two-stage and ABC overhead allocation methods, respectively; while that of the pump increased from $298.90 to $340.34 and, finally, to $359.48 when using the same three methods, in the same order, respectively. The result is quite fair when considering the complexity of the fuel pump, in terms of design and maintenance, when compared with the injector. Notice that using volume to allocate overhead costs results in over costing high-volume products, e.g. injectors (simple in terms of design and operation) and under costing low-volume products, e.g. pumps (more complex in terms of design and operation). The paper recommends to use ABC as a more accurate and fair method when charging maintenance job orders based on the analysis of costing two maintained items in the same premise while consuming different overhead resources.

Practical implications
– This study attempts to analyze different methods to calculate a specific corrective maintenance job order. It strives to remedy the drawbacks of the traditional overhead costing of a job order when using principles related to the size of service, such as the direct labor cost/hours, as an allocation base. Consequently, the study proposed a new costing method, i.e. application of ABC. The traditional costing approach is considered by many firms as the best costing method. Nevertheless, it allocates overhead cost over job performed uniformly (equally) not differentiating between the complexity of the job and variety of the activities performed, e.g. using the same allocation base for “oil change” and “fuel pump adjustment” activities. So, ABC prevents cost distortions (unfairness) that could not be prevented by traditional cost accounting system. The author believes that the method presented in this paper will provide a useful management tool for costing maintenance jobs based on the appropriate selected activity drivers in maintenance workshops. The method could be applied for costing maintenance activities in maintenance of all industrial sectors.

Originality/value
– The use of traditional costing method has proven to be distorted by applying overhead uniformly over different jobs of varied complexities and activities scope. In this paper the authors strive to present an effective costing alternative that outperforms the traditional ones with regard to overhead allocation. The paper aims to find reliable and fair maintenance costing method, i.e. to find out the relationships between maintenance activities and cost drivers. Although, ABC is widely used in manufacturing industry, no application or current research has presented an applicable thorough worked-out example, with the exception, to the author’s knowledge, of one in the aeronautical industry, to implement ABC method in maintenance industry. The importance of using this method comes from the fact that it provides, relatively, accurate and fair maintenance bills that provide customer satisfaction and firm good image. Hence, the paper is relevant in this respect and intended to contribute to the practice of maintenance management.