Right Sizing an Off-grid Solar House

Power reliability is one of the biggest concerns for people living off-grid. Current practice in off-grid solar house tends to either oversize solar power system or oversize the backup generator to ensure available electricity at all times, which often leads to a high system capital cost. Research has shown that right-sizing is essential to achieve a more efficient system with reduced energy consumption. Sound, responsible system sizing can only happen when liability issues become part of the design methodology, i.e. actively communicating with prospective owners/occupants regarding the risk that the thermal comfort, and full time use of appliances cannot be fully guaranteed. The risk of nonfulfilments may be related to extraordinary environmental conditions for a certain amount of time of the year, the chance that certain components will fail for some reason, and the fact that predictions of the operation of houses are based on design idealizations, whereas its real operation is to some degree uncertain. This paper presents a value-based approach to find the balancing point between the acceptable reliability level and the affordable system capital cost. The value-based approach is illustrated through a sizing practice of an existing off-grid solar house in Atlanta, GA.