This study investigates the design and optimisation of a hybrid plant comprising an array of 30 MWac PV-CSP modules. Each module integrates a PV system, a power tower CSP with thermal energy storage, and a gas-fired generator for backup power. This configuration aims to leverage the benefits of both PV and CSP technologies while addressing the challenges associated with large-scale CSP systems, such as high upfront costs and lengthy construction periods. A Python-based application was developed to optimise and simulate a modular PV-CSP hybrid plant. This application integrates existing software with custom computational and financial models to generate performance and economic metrics. To investigate the possible economic advantages of a modular plant, a single 120 MWac plant was compared with a modular plant comprising 4 × 30 MWac modules constructed sequentially. The large-scale plant demonstrates better economic performance across all investigated metrics. The modular layout enables earlier revenue generation; however, it has a higher total installation cost than the large-scale plant. These findings highlight the possible economic advantages of constructing single large-scale systems rather than integrating several small-scale systems.