The board of the Modesto Irrigation District voted Tuesday to buy electricity from a 160-acre solar project proposed for North McHenry Avenue.
The vote came over objections from several ratepayers, who said the price would be too high compared with conventional power.
MID officials declined to disclose the exact price in the 25-year contract, arguing that doing so could hamper negotiations for future projects.
A calculation by The Bee, based on information in MID documents, puts the price at about 17 cents per kilowatt-hour. That's roughly double the price of conventional power.
The McHenry project, the district's first major foray into solar, would be built by SunPower Corp. of San Jose. It still needs a permit from Stanislaus County officials.
The 25-megawatt system would meet just 2 percent of the MID's demand, but supporters said it would help protect the district from volatile fossil fuel prices and environmental rules.
"This is very rare — a local source of energy here in your territory, with no emissions," said George Petrulakis, a Modesto attorney working with SunPower.
Richard Anderson, representing a group called Sustainable Action Modesto, cited problems with coal mining and oil drilling to show his support for the project.
"Solar is more expensive than constructing another fossil fuel plant, but solar does not cause black lung disease nor kill 25 workers in an underground blast," he said.
Although the price per kilowatt-hour was not disclosed, district staff estimated the power would cost about $10 million a year over the 25-year term.
The system would produce about 59 million kilowatt-hours a year, which works out to 17 cents per kilowatt-hour.
The staff said a 1.4 percent rate increase could be needed in 2012 to cover the project's extra cost.
Dave Thomas, a leader of the Stanislaus Taxpayers Association, said the district should disclose the exact price.
"We've never said, 'This is a lousy project,' " he said. "We've said, 'What is it going to cost?' "
District officials said secrecy about prices is a common practice among power buyers and sellers, both of whom do not want the numbers to be known by parties involved in future projects.
The McHenry project would help the MID meet a state mandate to get at least 33 percent of its power from renewable sources by 2020. It stands at 12 percent, almost all of it wind, but could reach the target by 2012 with planned solar, wind and orchard biomass projects.
The mandate is aimed at reducing carbon dioxide and other emissions believed to be causing a general warming of the global climate.
Waterford area cattle rancher Larry Byrd said the solar project should wait until the outcome of a November ballot measure that would delay California's main rules on climate change.
"It scares me that we're going to do this," he said.
The project had been scheduled for completion by spring 2011 but will be delayed about 15 months so its environmental effects can be studied.
The system would consist of several thousand 8-foot-tall photovoltaic panels, which convert sunlight into electricity. The project site, half a mile on each side, would be screened by landscaping.
The panels would turn during the day to track the sun across the sky. This would match the output to peak demand, which is 4 to 6:30 p.m. on summer weekdays, said Greg Salyer, manager of resource planning and development for the MID.
The system would allow the district to reduce its use of an old, inefficient gas plant on McClure Road for peaking power, he said.
Bee staff writer John Holland can be reached at firstname.lastname@example.org or 5780-2385.