A new version of the SOLCHIPS predesign and optimization tool for solar heating systems with seasonal storage is described. The tool is based on analytical solution of the energy balance equations describing the system performance. It comprises a user-friendly interface with a minimum input requirement and is intended for preliminary system sizing and optimization purposes. The tool is here applied to the redesign of an existing solar heating installation and to the predesign of a completely new solar plant. The evaluation and dimensioning of one CSHPSS configuration can now be done in 10-20 s thus enabling fast optimization in respect to several parameters. A case study of an existing CSHPSS plant shows a 50% decrease in the annual energy price when the system is redesigned using the SOLCHIPS tool.