As one of the first U.S. states to open its doors to retail electric competition, California offers an important opportunity to assess the effectiveness of green power marketing as a mechanism for supporting renewable energy. This report is an interim assessment of key green power product, industry, and market trends in California. The report identifies and analyzes: the potential size of the green power market in California; the companies participating in the green power market; the green power products being offered and their prices; the impact of the green market on renewable generators and the environment; and the influence of several public policies and non-governmental programs on the market for green power. Data used in this paper have been collected, in large part, from surveys and interviews with green power marketers that took place between December 1997 and April 1998. There remain legitimate concerns over the viability of green power marketing to support significant quantities of renewable energy and provide large environmental gains, and it is far too early to assess the overall strength of customer demand for renewable energy. Nonetheless, initial evidence provided in this report suggests that: (1) the size of the green power market in the near-term will be limited, but its ultimate size is uncertain; (2) residential customers are the primary market for green power; (3) marketers that target the residential customer class are very interested in pursuing green power marketing, and customers have a large number of green products to select from; (4) the use of existing renewable resources has been the primary basis for green differentiation, but at least some of the products include meaningful commitments to new renewable energy generation; and (5) the price premium for green power is moderate, ranging from 0.7 cents/kWh to over 3 cents/kWh. For other states embarking on electricity restructuring and for renewable energy advocates, we believe that the early results presented in this paper are encouraging. It is important to recognize, however, that California has a market environment and set of public policies and market rules that, while not perfect, are more conducive to green power marketing than many other states. In fact, a critical finding of this report is that, because of the high cost of acquiring and servicing residential customers and the low utility default service price, green power marketing affords new energy service providers one of the only viable entrees to California's residential marketplace.