<Tr> <Td> r </Td> <Td>: </Td> <Td> discount rate </Td> </Tr> <Tr> <Td> n </Td> <Td>: </Td> <Td> expected lifetime of system or power station </Td> </Tr> <Dl> <Dd> Note: Some caution must be taken when using formulas for the levelized cost, as they often embody unseen assumptions, neglect effects like taxes, and may be specified in real or nominal levelized cost . For example, other versions of the above formula do not discount the electricity stream . </Dd> </Dl> <Dd> Note: Some caution must be taken when using formulas for the levelized cost, as they often embody unseen assumptions, neglect effects like taxes, and may be specified in real or nominal levelized cost . For example, other versions of the above formula do not discount the electricity stream . </Dd>

What is the most cost effective renewable energy source