This chapter is mainly emphasised on techno-ecnomics of the solar systems. It also included energy metrics of the system. The cost analysis, cash flow diagrams, payback time, net present value, benefit-cost analysis, effect of depreciation, etc. of the different PV/T have been described and evaluated using many of the solved examples. This type of analysis is used for project cost control, profitability analysis, planning, scheduling and optimization of operational research of the systems.