The efficient operation of induction machines and methods to estimate their working efficiency have received increased attention in recent years due to the growing awareness of the demand side energy management programs. Various techniques have been proposed for efficiency estimation with different requirements. Numerous works have also been published in the literature about estimating the efficiency of a machine in situ, under the loaded condition without disturbing its operation. However, very little has been done on estimation of the efficiency of the machines after the refurbishment process in the workshops, which in fact can affect numerous machines in the industry. In this paper, a method is proposed for this purpose, which requires only the no-load test. The proposed method is validated by experimental results with seven different induction machines.