Connection of electric storage technologies to smart grids will have substantial implications for building energy systems. Local storage will enable demand response. When connected to buildings, mobile storage devices, such as electric vehicles (EVs), are in competition with conventional stationary sources at the building. These EVs can change the financial and environmental attractiveness of on-site generation [e. g., photovoltaic (PV) or fuel cells (FCs)]. To examine the effect of EVs on building energy costs and carbon dioxide (CO2) emissions, a distributed-energy resources adoption problem is formulated as a mixed-integer linear program with minimization of annual building energy costs or CO2 emissions and solved for 2020 technology assumptions. The mixed-integer linear program is applied to a set of 139 different commercial buildings in California, and example results and the aggregated economic and environmental benefits are reported. Special constraints for the available PV, solar thermal, and EV parking lots at the commercial buildings are considered. The research shows that EV batteries can be used to reduce utility-related energy costs at the smart grid or commercial building due to arbitrage of energy between buildings with different tariffs. However, putting more emphasis on CO2 emissions makes stationary storage more attractive, and stationary storage capacities increase, whereas the attractiveness of EVs decreases. The limited availability of EVs at the commercial building decreases the attractiveness of EVs, and if PV is chosen by the optimization, then it is mostly used to charge the stationary storage at the commercial building and not the EVs connected to the building. DOI: 10.1061/(ASCE)EY.1943-7897.0000070. (C) 2012 American Society of Civil Engineers.