Buying pools may help encourage more green energy development. By combining consumers into one larger block, electricity suppliers say that they are able to leverage their buying power to bring down prices for all technologies, including renewable energy. In some cases around the country, cities are aggregating their businesses and households and buying renewable energy credits. Those "certificates" guarantee the production of such things as wind generation, thereby facilitating the development of more sustainable energy generation.

Consider Direct Energy, which has just completed a deal for 10 cities in Texas to buy almost 13,000 renewable energy credits over the next 15 years: The alternative energy provider says it will then purchase that energy and the associated credits from five West Texas wind farms, with a total output of 813 megawatts. That, it adds, will offset more than 2 million tons of carbon dioxide a year.

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