Powering cellular base stations with renewable energy are one of the long-term strategies for achieving green networks and reducing their operational costs. As an energy provider, the power grid is evolving into a smarter one, which allows more energy-efficient cellular networks and enables cooperation and interaction with the smart grid. On one hand, cellular networks can use harvested renewable energy and on-site energy storage to reduce their energy costs. On the other hand, the price of electricity depends on the energy load, which will eventually contribute to decreasing the peak consumption and global energy cost. In this paper, we propose new integration architecture for renewable energy-powered cellular networks and the smart grid. The proposed architecture is designed based on the classification and the analysis of the existing proposals and the requirements of the smart grid, renewable energy systems, and cellular networks.