Means the difference between the discounted revenues and the discounted operating costs over the economic lifetime of the investment, where this difference is positive.
ystyr "elw gweithredol" yw'r gwahaniaeth rhwng y refeniw wedi’i ddisgowntio a'r costau gweithredu wedi’u disgowntio dros oes economaidd y buddsoddiad, lle mae'r gwahaniaeth hwn yn un cadarnhaol.