Greater Los Angeles requires coastal power plants to ensure a reliable electricity supply through the end of the decade, according to emerging analyses by state agencies. The quest for regional generation is complicated by the state\u2019s requirement to phase out once-though cooling, the lack of smog offsets in the area, and the apparent long-term outage of the 2,200 MW San Onofre Nuclear Generating Station. An interagency team studying the needs of the area concluded that repowering a number of coastal power plants is necessary to meet demand, particularly in the heavily populated and industrialized western portion of the area, according to Mike Tollstrup, California Air Resources Board\u2019s project assessment branch chief. Coastal capacity is required because of the configuration of the region\u2019s transmission and distribution grid. The localized grid limits energy imports. The finding comes in the course of a study that the Legislature ordered in 2009 under AB 1318. Researchers also found that demand-side management programs could help cut the number of repowered units needed along the coast as long as the programs are as dependable as power plants themselves. Renewable energy also can help, but not eliminate coastal plants. The Air Board is conducting the study with assistance from the California Independent System Operator, California Energy Commission, California Public Utilities Commission, and State Water Resources Control Board. The western area of the Los Angeles region is expected to require at least 7,397 MW of local generating capacity controlled by CAISO in 2021, said Neil Millar, grid operator executive director of infrastructure development. Speaking in Los Angeles before the California Energy Commission June 22, he said the western area currently has 6,722 MW of CAISO-controlled capacity. Overall, the whole region will need at least 12,567 MW of local generating capacity in 2021, he added. It has 12,083 MW of capacity--if the San Onofre plant is counted. With planned retirements, this means adding a minimum of 1,870 MW of CAISO-controlled capacity by 2021 and potentially up to 3,896 MW, according to Millar. The precise amount depends upon factors like the degree of demand-side management, the advance of renewable energy, and evolving state environmental policies. If San Onofre never returns to service, those amounts would grow. Millar said the grid operator already is working on a \u201cleast regrets\u201d plan for how to make it through summer of 2013 without San Onofre. It\u2019s due in July. CAISO is studying the implications of the facility being permanently shuttered, even though it\u2019s licensed to operate into the next decade. The plant closed in January due to premature wear of new steam generator equipment, which caused a radioactive release. Los Angeles Department of Water & Power--which is not controlled by CAISO--also is concerned about the need to generate power along the coast, according to Mohammed Beshir, resource planning manager for the muni. It\u2019s cooperating in the AB 1318 study. The muni needs to keep virtually all its coastal power plants running to maintain reliability, according to Beshir. In 2021, Los Angeles expects to require at least 3,471 MW of local generation capacity to meet customer needs. The muni currently has local generating capacity at four gas-fired plants totaling 3,415 MW. He explained the muni is moving to repower all of its coastal units by 2029, nine years beyond when the state wants Los Angeles to phase out use of once-through cooling. During that time, he said, the muni hopes to keep all its existing plants running while new units are built on the same sites. A key concern in repowering existing plants is the shortage of emissions offsets, said Barry Wallerstein, South Coast Air Quality Management District executive officer. It also could affect building new ones in the eastern part of the Los Angeles region where air-conditioning use is heavy due to hot summers. He said three planned projects--Sentinel in Coachella Valley, Walnut Creek in the City of Industry, and NRG in El Segundo--need 1,998 pounds\/day of offset credits for fine particulate matter, while the open market supply is just 911 pounds. New power plants and industrial facilities have to offset their emissions under the federal Clean Air Act and state environmental laws. Competitive Power Ventures is building the 850 MW Sentinel facility under a state law giving it a special dispensation for offsets. Edison Mission Energy\u2019s 500 MW Walnut Creek project is relying on credits from the shutdown of Huntington Beach units 3 and 4--although they\u2019re being fired up again this summer to make up for loss of San Onofre. Huntington, with 452 MW of generating capacity, is owned by AES. NRG\u2019s 550 MW repowering project at the company\u2019s El Segundo plant is able to use internally held credits. To alleviate the credit shortage in the face of the apparent need for new fossil-fuel fired capacity in the Los Angeles region, the AB 1318 report may include recommendations to the Legislature to change state clean air laws. After being issued in draft form for public review later this summer, the Air Board plans to send it to the governor and Legislature this fall.