The calculation of LCOE can be complicated because some costs are incurred immediately (i.e. so-called 'overnight costs', such as the capital cost to build the plant) and other costs are recurring costs (i.e. future annualized costs, such as the O&M cost) over the plant financing period. So to calculate the LCOE, either the capital cost must be converted to annualized costs, or the annualized recurring costs must be converted to present costs.