As a result of the world's rapid socioeconomic growth and environmental concerns, exploring diverse energy resources besides fossil fuel has become a necessity and not an optional mission. Even for the oil wealthy nations, adopting energy-mix policy has become a strategic goal that is profoundly sought. As preliminary outcome, investments in renewable energy source (RES) systems in arid region nations have taken tangible steps in planning and policy making. RES has several appealing factors; however, most countries where regulated or vertically integrated electric power systems are the principal methods for supplying the demand are cautious. Most of the electric utilities in these countries are putting reservations on RES due to the lack of monitoring and control of these grid-connected RES systems that might contribute to the instability of the electric grid. This paper identified the challenges and concerns of grid-connected RES. Moreover, it presented possible RES interconnection management schemes for the vertically integrated electric power systems. (C) 2009 Elsevier Ltd. All rights reserved.