When a solar energy system is designed, the engineer seeks to find a solution that gives the maximum life cycle savings of the installation. Such savings represent the money that the user/owner will save because of the use of a solar energy system instead of buying fuel. To find the optimum size system that gives the maximum life cycle savings, various sizes are analyzed economically. When the present values of all future costs are estimated for each of the alternative systems under consideration, including solar and non-solar options, the system that yields the lowest life cycle cost or the maximum life cycle savings is the most cost effective.