As shown in Figure X below, the ratio of module cost to non-module cost (BOS) is approximately 3:2 . The projected reduction in system costs through 2020 will be significant, approximately in half, due to economies of scale resulting from improved module and non-module manufacturing technologies. The reduction would then be slower as the percentage of soft costs to total system cost increases proportionally. deemed to have been consumed or expired, and thus becomes an expense. Table X below shows the ownership costs of lithium-ion batteries. Table , DOD (%) 80Cycle load efficiency, η (%) 90Source: .Depreciation charge can be calculated as: δ=Capex/(Lifetime*Cycles per day*365*DOD* η) =800/( 10*1*365*80*90) = S 0.30 $/kWhAt this price, it makes more sense to sell the surplus electricity produced rather than storing it for later.