Chiết khấu của tất cả các dòng tiền xảy ra trong giai đoạn nghiên cứu một lựa chọn dự án là việc tính toán cơ bản cần thiết cho máy tính giá rẻ. Các quyết định liên quan đến một trong những lựa chọn một nhóm các lựa chọn thay thế loại trừ lẫn nhau nên được thực hiện bằng cách sử dụng giá rẻ. | Figure 15-3. Present Value Factors Used in Federal Energy and Water Project LCC . Making Decisions With LCC Analysis . Lowest Total LCC Discounting of all cash flows occurring over the study period for a project alternative is the basic computation needed for computing LCC. Decisions regarding selection of one of a group of mutually exclusive alternatives should be made using LCC. The alternative with the lowest LCC over the study period is the appropriate choice. These decisions are typical in planning for new construction. For example Which lighting system should I choose for a new building Should I specify R19 R25 or R30 insulation. Which of these HVAC system alternatives should be specified Which combination of building envelope measures lighting system alternatives and HVAC system selection should I choose In each case the answer is the alternative or combination of interdependent systems that has the lowest LCC over the study period. In retrofit analyses the first decision to be made is typically Should this possible retrofit project be accepted or rejected In this case two alternatives are being compared. The base case or the do nothing alternative -- maintaining the status quo is compared to the recommended measure. If the proposed retrofit has a lower LCC over the study period than the base case then it should be recommended. . Payback Period Usually the economic difference between two alternatives is expressed in terms of payback or how long it takes to recover the additional investment cost. In this example the investment cost is the first cost of the proposed retrofit and assuming uniform annual cash flows the annual savings is the difference between the O M costs before and after the retrofit. Simple Payback SPB relates how long it takes to recover an initial investment in a cost-saving measure assuming the annual savings remain constant and that the time value of money is unimportant. To calculate SPB simply divide the initial .
