Assessing the cost accuracy of electrical works towards sustainable procurement of building services

The inaccuracy of cost forecast for building services has being ascribed to the practice of allocating deterministic lump sum figure from historical data, as opposed to making detailed measurements. Using a quantitative research approach based on the analysis of project data, this study provides statistical evidence to reinforce this view point various researchers have embraced over the years. The study investigates the current practice and the levels of accuracy attainable with the cost estimation practices for electrical installations currently deployed in Port Harcourt, Nigeria. Cost data from one hundred and sixty-one Bills of Quantities are collated and statistically analyzed. The outcome of the research shows that an average of 65.83% of bills prepared by quantity surveyors for electrical installations, sampled within a six-year period, were computed using provisional sums while a percentage relative to 34.17% were measured in detail. The findings further showed statistically significant association between the method of estimating and level of accuracy. With significant disparity in the levels of accuracy of provisional sums allowed for electrical installations in bill of quantities (24.35%) compared to estimates generated through detailed measurement (9.77%). The study outcomes reinforced the need for systematic cost breakdown and financial management of electrical works in the procurement of buildings.