# Understanding Microgrid Sustainability: A Systemic and Comprehensive Review
## 5 Financial Field
### Financial Issues  
The literature points to three critical financial issues that must be addressed to ensure the economic sustainability of a microgrid: techno-economic design, management, and long-term planning [10; 18; 179; 200].  
Techno-economic design is based on the calculation of the Levelized Cost of Energy (LCOE) of the microgrid based on the sum of its costs (Capital Expenditure (CAPEX), Maintenance and Operational Expenditure (OPEX)) and the forecast of produced energy [51]. The challenge of techno-economic design is that there are assumptions regarding inflation, discount rates, downtime, and consumer payment default among others, which can alter the analysis of the feasibility of a microgrid. Many studies address the problem of rightly estimating the LCOE of a microgrid by highlighting the importance of a preliminary feasibility study of the microgrid [52; 53], providing a rigorous framework [54], estimating the correct business model [56], and evaluating the different constraints [55] to better understand the local context and user needs. The same goes for taking into account good practices that have been identified in different case studies to make better assumptions when estimating the chances of success of new microgrid projects [69; 201]. Finally, some studies go a little deeper by providing complete models for microgrid deployment [202], systemic methods for microgrid design [51; 203], or techno-economic optimization frameworks [204; 205].  
Management handles the day-to-day cash flow of the microgrid [57; 58; 59; 60], and it can be summarized as maintenance and collection of payments [61; 62]. Maintenance costs money but is imperative for the operation of the microgrid. It requires trained and qualified personnel together with the proper equipment [10; 62]. The collection of payments provides money to the microgrid but requires a particular organization and staff to ensure its correct execution [19; 206; 207]. More intelligent microgrids have automated and optimized payments, which greatly facilitate collection [208; 209].  
Long-term planning is at the same time forward-looking and backwards-looking in nature [63].  
Forward-looking planning tries to anticipate and smooth transitions, especially if the acquisition of new equipment and expansion is involved [64; 65]. Backwards-looking planning inventories are recurring problems that must be addressed when new investments become necessary [7; 66; 67]. The literature has proposed several methodologies to guarantee the integrity and the execution of the planning process [210; 211].  
The financial issues change over time and can be seen through a before, during, and after deployment framework. Before deployment, a techno-economic study must address the most relevant aspects of ownership and governance to minimize the LCOE of the microgrid and maximize its likelihood of success. During deployment, management must strike a balance between minimizing maintenance costs, providing good service, and maximizing payment collection. Post-deployment refers to long-term planning that anticipates investments to replace equipment and expand services while keeping the LCOE low.