12.4 THE Pa, P. METHoD
Another way of viewing the calculations of Example 12.7 is to obtain the present worth of each column and sum them to obtain the present worth of solar savings, using appropriate signs for each column. Therefore, the life cycle savings(LCS) of a solar energy system over a conventional system is expressed as the difference between a reduction in the fuel costs and an increase in expenses incurred as a result of the additional investment required for the solar energy system, given by