CASE STUDY

Granite Construction

Location

Stockton, CA

Facility Type

Construction Plant

Solutions​

Energy Storage, Utility Bill Optimization

Commercial Operation Date

August 2018

Energy Storage System Size

220 kW / 880 kWh

Actual 1-Year Savings (Site)

$85,000

Actual 1-Year Savings (Fleet)

$860,000 (in 2020)

Company Achieves $860K in Savings with Stem Energy Storage – In One Year

Granite is America’s Infrastructure Company™. Incorporated in 1922, Granite is one of the largest diversified construction and construction materials companies in the United States as well as a full-suite provider in the transportation, water infrastructure and mineral exploration markets serving North America and Guam.

Faced with rising demand charges and changing rate structures, Granite pursued energy storage to gain the flexibility to buy energy at the most inexpensive times and use stored power when costs are higher. An asphalt provider to contractors and municipalities in the Stockton, California area, Granite first installed Stem energy storage at its French Camp site, near Stockton, in 2018. The success of that project moved Granite to install Stem systems at four other locations. In 2020, Stem’s Athena™ smart storage software saved Granite $860,000 on utility bills.

Challenge

Historically, Granite accumulated high monthly power demand charges from PG&E during the plant’s normal operational hours. In order to reduce energy costs, they interviewed multiple energy storage providers throughout California. However, repeated discussions with other providers to design, install, and maintain battery storage showed that although many could provide similar-looking storage systems, they all lacked smart storage software capabilities. This would be essential to help automate demand charge management and utilize the batteries to best reduce costs.

Granite also needed a provider who could work with multiple California utilities – including PG&E, SoCal Edison, and SDG&E – that span their other statewide construction plants. Many providers, they found, worked only in one utility’s service area.

Solution

Granite ultimately chose Stem because of our knowledge of battery systems and installation expertise throughout California with various utilities.

Stem’s Athena software was also a factor. As Aaron Vasbiner, Plants Manager for the Valley Region, explains, “We selected Stem because we have confidence in the intelligence of Stem’s energy storage controls.”

Granite’s French Camp construction plant provides asphalt even when power costs are very high. So, Athena’s demand management capabilities were ideal for Granite to switch to stored battery power and use less grid-supplied power in order to save on energy costs. The batteries then recharge overnight, when energy costs go down.

Athena’s predictive analytics combine tens of thousands of historical, forecasted, and real-time data points, including market data and local weather forecasts, to optimize dispatch of Stem battery systems. Given the importance of peak prediction, Athena leverages multiple forecasts and continually analyzes actual vs. forecasted peaks to further hone its accuracy.

Results

In 2020, Stem’s Athena smart storage software saved Granite $85,000 at the French Camp location and $860,000 across all five of its Stem systems. More installations are in progress.

Granite acknowledges that Athena is key to making the energy storage system function, as its AI capabilities monitor grid conditions and automatically switch the construction plant to run on battery power during peak demand times.  

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