Energy harvesting is becoming one of the most important issues today due to the fast depletion of conventional energy resources. Current research efforts focus on efficient and reliable use of renewable resources such as solar, hydro, wind, and thermal resources to provide environmentally friendly solutions while minimizing the cost. However, an efficient and effective delivery of green energy to individual households remains a challenging issue. One key roadblock is the high complexity of the smart grid system. In this paper, we propose a new interface theory based energy-timing model for smart homes and smart grid management and design. This model allows simple yet accurate computations for energy supply and consumptions involved with photovoltaic (PV) cells, storage units, and load appliances for each home. At community, and city or state level (or nationwide), this model also has the potential to facilitate fast and effective energy management, optimization, and load scheduling. The end result is the possibility of managing smart grid with millions of households to achieve low cost and high energy savings.