## 1 Introduction  
Rapid advancement in state-of-the-art technology naturally leads to the need for development of more stable, reliable, and efficient methods to harvest electrical energy. Real-time alignment and synchronization between supply and demand is necessary since electrical energy is hard to store. To overcome this disadvantage, the system needs to have a certain amount of reserved power. Recently, Photovoltaic (PV) and Energy Storage Systems (ESS) have been mentioned as the possible solution to such problems. The importance of renewable energy is rising with new regulations from the United Nations Framework Convention on Climate Change (UNFCCC) and the increasing price of fossil fuels.  
The Korean government is making the installation of ESS mandatory in public institutions. Not only do ESS systems work as an emergency electrical system and boost efficiency by saving on the electricity produced, they are also at the core of electric cars and power demand management.  
Especially, governments around the world have a greater interest in the stability of the power grid and in the efficient usage of renewable energy after severe power blackout experienced around the world in beginning of the 21 st century. Studies have been done to inspect how installation conditions of PV systems [1] and environmental elements could influence the output of PV systems [2], however there are still various characteristics that have a high probability of causing instability in power systems, such as random shadow casted on the PV module causing power loss [3], and this is a great setback in increasing the amount of energy generation. ESS-connected PV systems are nowadays actively used to compensate for such problems. Currently, ESS-connected PV with the highest renewable energy certificate (REC) of 5.0 [4] are being installed. When installing ESS, it is important to choose the right capacity that is suitable for the PV system while considering its capacity, generation time, maximum load, etc. If those conditions were not reviewed, then over or under estimation of PV and ESS system would occur, which resulted in over price or shortage of electricity. [5] Under the governmental policies, it would be difficult to achieve realistic conditions and result in over-estimated size of PV-ESS system. Study has been done to solve this problem by deriving optimized capacity of PV and ESS, while considering the power consumption of each household [6]  
In the recent past, the investment in PV systems and wind power has been increasing every year. This is the result of rapid growth in the PV industry in China, which has the world's biggest market economy. PV systems are expected to have a far bigger annual production as compared to other energy sources for the next five years while considering all of these aspects [7].  
This study investigated investment costs and completed case analyses when PV and ESS are deployed in buildings that cannot afford optimized capacity calculations and economic evaluations. Next, we developed an economic evaluation algorithm, which can minimize the time before where a return on investment (ROI) is evident that can be applied to various cases. Based on this algorithm, the policies of the current government in supporting renewable energy initiatives were reviewed. This paper is a case study for national strategy of South Korea with specific LCOE, incentive policies, PV installation cost, etc.