AbstractCentral Solar Heating Plants with Seasonal Storage (CSHPSS) are systems producing heat from solar radiation for a district heating system. These systems are able to produce thermal energy during all the year providing a significant part (high solar fraction) of the demands required for space heating and Domestic Hot Water (DHW). The design and calculation of the behaviour of these systems during the year is a complex process requiring detailed climatic and demand data in order to properly design/sizing the plant components to reach the desired behaviour (e.g. a specific solar fraction). The location of the plant and the different demands corresponding to different climatic areas affect very significantly the behaviour of these systems. As a consequence, the sizing and design criteria of the pieces of components of these systems are very different in the North and the South of Europe.The utilization of simple methods for the calculation of these systems allows the design of the main components and provides an estimate of the behaviour of the system during the year. In this paper is proposed a simple method for the calculation of CSHPSS using demand data and simple and easy to find available public climatic data. The proposed method is completely described and applied to specific Spanish locations to pre-design the main components of these systems. The model also provides a preliminary economic evaluation of the system and is very useful to perform parametric analysis to evaluate the CSHPSS system performance, as well as to establish optimization and design criteria of CSHPSS.