An evaluation of the level of accuracy of electrical services cost estimates in Nigeria

The increase in the quality and standard of living has affected the way and method buildings are being designed and constructed all over the world. Consequently, the design of electrical services in building projects is becoming more complex thereby creating large cost management gap in the overall pricing of electrical works. The cost significance of this element is constantly increasing and the cost estimates produced for electrical services have not been satisfactory. This paper examined the method used for the production of cost estimates for electrical engineering works in Nigeria and determined the level of accuracy. Questionnaires were administered to 225 electrical engineering estimators in contracting and consultancy firms, out of which 158 questionnaires were retrieved. Consultants' cost estimates and tender sums submitted by contractors for the same projects constructed in Lagos and Abuja between 1993 and 2003 were also collected for 89 projects out of which 80 were appropriate for analysis. Relative Importance Index (RII) and Coefficient of Variation (CV) were used to analyze the data collected. The results showed that the most frequently used method of estimating was the Superficial Area method and that the estimators sourced their cost data through market survey, use of cost data files and priced Bill of Quantities of similar projects. The results also revealed that the mean CV for electrical engineering works was 16.70% which was not within the range of 5% - 9% specified as acceptable. The paper concluded that the method of estimating used for the production of cost estimates for electrical works was inappropriate and that the estimates produced were inaccurate.