In the diploma work, we first make an overview of some programs for the design of solar power plants that are accessible online. Then, we focus on the Sunny Design 3 program developed by SMA company. The objective of the project was to acquaint itself with the program and to make a plan for a small solar power plant to cover the annual demand for the electricity of a dwelling house. All procedures necessary for the preparation of the plan and the selection of the basic building blocks of the plant are described. In the end, we also present calculations regarding predicted energy production of the plant.