Solar energy is increasingly recognized as an important future energy source due to its abundant availability and renewable nature. However, the intermittent nature of solar energy can cause fluctuations in the produced electricity, making it difficult to guarantee a stable and reliable electricity supply. One solution that can be implemented is to use batteries in a photovoltaic solar power plant system with a Simple Moving Average (SMA) control algorithm, which can help in smoothing and reducing fluctuations in the solar power. The parameter that can be adjusted in the SMA algorithm is the Window Size (WS) or the arithmetic averaging width of the photovoltaic output power over time. This research evaluates the effect of changing WS value in the SMA algorithm on the resulting smoothed photovoltaic output power, and the technical effects on batteries. Based on the results of evaluation, the increase of WS value will slow down the response of photovoltaic output power to changes in irradiation and increase the smoothing quality of the intermittent photovoltaic output power. In addition, increasing the WS will reduce the maximum power received on the load side, and the amount of energy used by the battery during the power smoothing process will increase, resulting in the increase of required battery capacity. © 2024 IEEE.