The paper is devoted to a comparison of open source power flow solvers: Pandapower, PyPower, PyPSA, GridCal, and a custom-developed solver. The core objective was to evaluate and contrast their performance in solving the power flow problem. The widely-used Newton-Raphson method has been tested as the primary analytical tool across all solvers, focusing on two primary metrics: computation time and the number of iterations required for convergence. The analysis was conducted under standard operating conditions, followed by stress-testing scenarios, where the solvers' resilience was examined under increased load conditions.