Sempra Generation and Pacific Gas and Electric Co. (NYSE: PCG) reached a power-purchase agreement for the planned second, 150-megawatt (MW) phase of Sempra’s Copper Mountain Solar project. Under the 25-year agreement, the Sempra Energy (NYSE: SRE) subsidiary will sell power generated at the site to PG&E.

“Ultimately, we have two solar projects out there now. El Dorado Solar is a 10-megawatt PV array. Copper Mountain Solar 1 is a 48-megawatt system,” said Sempra spokesperson Scott Crider.

Both of those systems are under power-purchase agreements with PG&E, he said. As with the previous installations, Copper Mountain Solar 2 will be built by First Solar Inc. (NASDAQ: FSLR) using its modules, he said.

Construction on project is slated to start in early 2012, according to Sempra. The second phase will be brought online in two parts. The first 92-MW part of the plant is expected to come online in January 2013. The remaining 58 MWs are expected to be online by 2015.

However, PG&E could choose to speed up the implementation date based on its renewable energy requirements under California’s renewable portfolio standard, Crider said.

“It provides PG&E with some flexibility,” he said. “This first phase will help them achieve their interim goals very quickly. If they decide they need some additional power to meet their obligations sooner than 2013, then we can start construction immediately. It’s certainly one of the advantages we have as a developers.”

El Dorado was built in 2008, according to Crider.

“The size of these installations is just growing exponentially,” he said. “To put it in perspective, in 2008, [El Dorado] was the largest PV plant in North America.”

Since Sempra is building up a portfolio of large solar projects—like the Copper Mountain Solar projects and 150 MWs of solar it’s building in Arizona—it’s been gaining experience in the solar installation industry, according to Crider.

“As we gain the experience, in construction and deployment,” he said, “it really helps us distinguish ourselves among our competitors.”

The company has been building in improved efficiencies on the construction side.

“We have been able to deliver our projects as promised,” Crider said. “An advantage of PV is it’s almost like an assembly line. It’s almost a continual construction process for us.”

Image courtesy of Sempra Generation.