Optimal battery sizing studies tend to overly simplify the practical aspects of battery operation within the battery sizing framework. Such assumptions may lead to a suboptimal battery capacity, resulting in significant financial losses for a battery project that could last more than a decade. In this paper, we compare the most common existing sizing methods in the literature with a battery sizing model that incorporates the practical operation of a battery, that is, receding horizon operation. Consequently, we quantify the financial losses caused by the suboptimal capacities obtained by these models for a realistic case study related to community battery storage (CBS). We develop the case study by constructing a mathematical framework for the CBS and local end users. Our results show that existing sizing methods can lead to financial losses of up to 22%.