In this paper, we introduce a tile-graph-based approach to power planning. For a given flooplan solution, the power inputs are modeled into a tile graph, the minimum capacity of each power input and the maximum power need of each module in a floorplan are accumulated in an associated tile. An efficient cost evaluation algorithm is adopted to calculate the cost of power planning. As its computation time is quite short, it is reasonable to integrate such an algorithm into an iterative floorplanning environment.