Comparison of Shared and Separate Transformer Designs in Building Solar PV Systems

Abstract

This study aimed to analyze the impact of transformer configuration on buildings equipped with solar photovoltaic (PV) systems by comparing two approaches: the shared transformer configuration and the separate transformer configuration. In many practical building installations, all electrical loads and PV generation are routed through a single transformer, which can result in increased energy losses and
a higher risk of service interruption. The analysis focused on four key engineering aspects: 1) energy delivery to the load, 2) line and transformer loss analysis, 3) load continuity and system reliability, and 4) total system cost. The evaluation was conducted using fundamental electrical engineering principles, including the transformer efficiency equation, the current loss relationship in distribution lines, and a total system cost estimation model. The results indicated that the shared transformer configuration provided superior energy efficiency and lower overall system cost. While the separate transformer configuration ensured higher system continuity and reliability, making it more suitable for buildings with critical loads such as hospitals and data centers. Moreover, the separate transformer configuration provided greater flexibility for future integration of energy storage systems (ESS) and smart grid functionalities through independent power-flow