The tilt angle and row spacing are crucial parameters in the planning and design of Photovoltaic (PV) power plants. This study, aiming to minimize the Levelized Cost of Energy (LCOE) per unit land area, optimized the tilt angle and row spacing for fixed monofacial and bifacial PV arrays. To accurately reflect the effect of tilt angle and row spacing on the objective, algebraic expressions for calculating the front and rear sides irradiance of PV arrays considering tilt angle, row spacing, and shading effect in multi-row scenarios have been established. Based on the voltage-power (UP) characteristics of the PV array under local shading, a simple calculation method for the output power of the PV array was established under Inter-Row Shading (IRS) considering electrical characteristic. Multiple scenarios were established based on practical application conditions, and the Nelder-Mead optimization algorithm was employed to find solutions. The results demonstrate that the optimized LCOE is not only 0.75%–3.06% lower than that of the winter solstice rule (Standard rule) but the electricity generation per unit land area is also increased by 22.16% ∼ 50.79%. Additionally, this study provides a detailed analysis of various factors influencing the selection of tilt angle and row spacing for PV arrays. And comparing the differences and similarities in the impact of these factors on monofacial and bifacial PV modules. These contributions aim to provide a more comprehensive understanding and practical approach to optimizing the spatial arrangement of PV arrays, addressing key challenges in the field. •Algebraic expression of PV arrays irradiance calculation under IRS at any tilt angle, row spacing.•PV arrays power calculation under IRS is simpler by analyzing the UP curve under local shading.•Optimization model for the spatial arrangement of PV arrays considering IRS's impact on power.•Improvement more than 22.16% in lifecycle electricity by optimal spatial arrangement in a real case.