Abstract In this paper, a load flow calculation method for a radial distribution system is developed. The proposed method, which is derived from a Z-loop analysis, is very straightforward and simple without unnecessary mathematical approximations. It requires the same storage size as the Gauss-Seidel method, but less computation time than the conventional Newton-Raphson program. It is attractive for accurate or approximate off-line and on-line routines and contingency calculations for radial systems. The proposed solution algorithm can be implemented directly and efficiently into microcomputers with limited storage capacities. To examine the effectiveness, three normal radial distribution systems for 13-, 22-, and 58-bus systems were studied by the proposed method, and the convergence characteristics of a 43-bus ill-conditioned system are compared with the Newton-Raphson method. The proposed method is recommended for distribution system load flow analysis.