Inversion encoding is an encoding technique used to encode bus transmissions in low-power systems. It is typically utilized to save energy by decreasing the number of transitions on the bus. When the data is transmitted into the bus, the conventional method adds an INV signal to indicate whether the data is inverted. The method reduces the average and the maximal number of transitions and results in the reduction of average and peak power dissipation. However, the method still has room for improvement. We propose an efficient inversion encoding method by adding $k$ INV signals on bus transmission to achieve a smaller average number of transitions, which is supported by the results of the numerical calculations.