Instead, the event, which conveniently coincides with the 50th anniversary of the opening of the world’s biggest hot rocks network at the nearby Geysers, is tinged with uncertainty.

Along with the state’s wider renewables industry, the geothermal sector fears a “yes” vote on 2 November to California Proposition 23.

This poll, pushed by a host of Texas oil companies and trucking interests, threatens to overturn the state’s 2006 Global Warming Solutions Act on the grounds that it is “unaffordable” in a time of recession.

It