The present study investigates the optimal PV cell coverage ratio in terms of the overall energy consumption of office buildings in central China for which semi-transparent photovoltaic facades have been implemented, with various combinations of architectural variables including room depth, window-to-wall ratio (WWR), and orientation. Here, models and methods are established for the calculation of PV cell coverage ratio for a single-glazed semi-transparent PV facade and these models and methods are validated through field experiments. The established techniques are then incorporated into Energy Plus to perform a parametric analysis of the effects of different PV cell coverage ratios on overall energy consumption. The results show that PV cell coverage ratio has a pronounced effect on electricity consumption and that its impact is influenced by different combinations of room depth, WWR, and orientation. Moreover, the selection of an optimal PV cell coverage ratio is found to be an important element of the design approach in building-integrated PV (BIPV) systems: use of the optimal PV cell coverage ratio can achieve overall energy consumption savings of 13% (on average) compared to the least favourable PV cell coverage ratio. (C) 2014 Elsevier B.V. All rights reserved.