Sonoma County has received bids from 11 firms vying to be the electricity supplier for the proposed county power agency. It has refused to publicly reveal the bids, but said it has identified a "core group" of five or six.

Calpine Corp., the Houston-based operator of The Geysers geothermal field.

Shell Energy North America, which has the contract for the Marin County power agency.

Iberdrola, a multi-national electric utility company based in Spain, with operations throughout New England and New York state.

Noble Americas Energy Solutions, a large U.S. energy retailer based in San Diego.

NRG Energy, based in Houston and Princeton, N.J., one of the country's largest power producers and retailers.

Greensparc Energy Advisors, a San Ramon- and Sacramento-based power development and management firm.

Direct Energy, an energy retailer based in Canada and the U.S., a subsidiary of the British multinational corporation Centrica.

Promet Energy Partners, a natural gas and electricity supplier based in the Midwest.

ConEdison Solutions, based in Valhalla, N.Y., a subsidiary of Consolidated Edison.

Constellation, a power and natural gas supplier and subsidiary of Exelon, the Chicago energy producer, trader and distributor.

Plumas Rural Services, a nonprofit organization in northeastern California.

Source: County of Sonoma