This is the twelfth and final installment in a series of columns that discuss the design, construction and operation of the Equinox House, a net zero energy residence located in Urbana, Ill, powered by a grid-tied solar photovoltaic array designed to supply 100% of its annual energy requirements. This installment reviews the life-cycle costs for major elements such as windows, insulation, solar photovoltaic systems and infiltration. The entire series is available at ashrae.org/solarnzebproject.