Photovoltaic power generation and wind power generation have an advantage that energy is clean and infinite, but they have a disadvantage in that electrical output energy is unstable, and initial and maintenance costs are expensive. This paper presents an optimal configuration for renewable generating systems in residence using a genetic algorithm (GA). We define that the objective function is the total cost, where the total cost is the sum of initial cost, an operation cost, and a maintenance cost. We determine an optimal configuration of renewable generating systems, where total cost is more reasonable using GA. The simulation using this technique is shown.