The estimated cost of integrating 12,000 MW of distributed rooftop solar and other renewable resources by 2020, as called for by Gov. Jerry Brown, is between $600 million and nearly $3 billion, according to a California Energy Commission consultant report. The costs \u201cvary dramatically,\u201d Eugene Shlatz, with Navigant Consulting, said during an Energy Commission Aug. 22 workshop. It depends on where the generation is built and how it feeds into the power system\u2014including whether projects are clustered. \u201cHow might other technology enable [distributed generation] at a lower cost, address constraints and expedite the process?\u201d Shlatz asked. It was noted during the workshop that energy storage is part and parcel of an increased renewable distributed generation scenario but its cost effectiveness, including an agreement on how to define that, remain unresolved. The Navigant study focuses on how to lower integration costs, including factoring in future technologies. The Energy Commission sponsored analysis aims \u201cto gain a better understanding of utility system costs and impacts associated with increased [distributed generation] installations in California, and how those costs and impacts change based on interconnection location, distribution feeder characteristics, load types, and project size,\u201d stated the agency. \tDistributed generation integration costs arise from technical and physical challenges, including aging infrastructure, project siting issues, including environmental impacts, and the fluctuating ebb and flow of solar and wind power. The costs are estimated by Navigant to range from $130\/kW to $600\/kW. A key factor in price is whether and how many projects are built in urban versus rural areas. \tRural circuits generally are longer, which creates the potential for line overloading and thus the need for mitigation, Shlatz explained. But there is more available acreage for projects. In contrast, urban distribution system--lines and feeders--are more robust, with parallel systems to beef up reliability in population centers, he added. At the same time, space is limited in urban centers. \tTo date there are 3,300 MW of installed distributed renewable projects, reported Matthew Coldwell, with the Energy Commission\u2019s Electricity Analysis Division. An additional 1,200 MW would have to be added each year to reach the 2020 target of 12,000 MW. \tThe DG integration analysis discussed this week at the Commission fed off of a May 2012 study by Southern California Edison, The Impact of Localized Energy Resources on Southern California Edison\u2019s Transmission and Distribution System. That study looked at the impact of 4,800 MW of distributed renewables in the utility\u2019s territory. The Edison and broader Energy Commission analyses look at the impacts of increased numbers of renewable projects, generally 10 MW and smaller, which are near load pockets, can feed into utility distribution systems and are not dependent on costly new transmission. They\u2019re also supposed to be environmentally benign. Under the governor\u2019s directive, solar, wind and other non fossil projects up to 20 MW count towards his 12,000 MW goal. But in practice, projects generally are half that size or smaller because of voltage feeder limitations. \tThe allocation of the ultimate integration costs of 12,000 MW of local renewable projects and their impact on ratepayer bills were not analyzed, noted the commission\u2019s Coldwell. Also not factored in was the potential cost of transmission upgrades. That latter issue is challenging because there is no clear distinction between the lower voltage distribution lines and high voltage transmission lines. \tThe Energy Commission and California Public Utilities Commission are working on a study evaluating how a \u201csmart grid\u201d can improve the management and operation of large inflows of distributed generation into the electrical system. However, the cost of an advanced digitized grid is not part of that stud. \tA revision of the draft Navigant study on the integration costs of 12,000 MW of distributed generation in California is expected to be released next month.