Press release: California adopts nation’s first advanced inverter standards - Clean Coalition
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Press release: California adopts nation’s first advanced inverter standards

Decision modifies interconnection rules to secure benefits offered by advanced inverters.

Craig Lewis

January6, 2015

NEWS RELEASE:California adopts nation’s first advanced inverter standards

Decision modifies interconnection rules to secure benefits offered by advanced inverters

San Francisco, CA –On December 18, 2014, the California Public Utilities Commission (CPUC) adopted Recommendations for Updating the Technical Requirements for Inverters in Distributed Energy Resources, which establish new standards for advanced inverters under California’s electric interconnection tariff known as Rule 21.

“Enabling the full suite of advanced inverter functionality is essential to bring high-levels of distributed generation online quickly and cost-effectively – in California and every other leading market around the world,” said Craig Lewis, Executive Director of the Clean Coalition. “These new standards anticipate the needs and capabilities of the distribution grid as penetration levels of local renewables increase.”

Advanced inverters offer significant benefits to the power grid, including improved reliabilityand efficiency. They alsosupporteasier and lower cost interconnection of distributed generation because of their ability to monitor and respond to grid conditions.Specially, advanced inverters enhance grid operations by:

  • providing fast-acting local grid support in response to changes in voltage, frequency, and power requirements
  • allowing distributed generation facilities to provide local voltage support along feeder lines, mitigating both under and over-voltage
  • providing increased visibility into the operating characteristics of the distribution grid
  • supporting both autonomous response to grid conditions and controlled response via centralized utility commands
  • offering significant potential for reducing system upgrades required to support higher penetrations of distributed generation, while also simplifying and accelerating interconnection studies

Through leading efforts to update California’s Rule 21 Distribution Interconnection Standards, contributions to California’s 2012 Integrated Energy Policy Report, and involvement in the Smart Inverter Working Group, the Clean Coalition pushed for the adoption of advanced inverters and the creation of standards to bring the full value of these functions to the grid. The CPUC ‘s December ruling builds upon a multitude of Clean Coalition recommendations and makes California the first state in the country to require the use of advanced inverters with distributed energy resources.

Under the ruling, California’s investor-owned utilities must install advanced inverters the later of December 31, 2015, or 12 months after the date that the Underwriters Laboratory approves new certification standards regarding: default voltage ride-through requirements; anti-islanding protection for new voltage ride-through settings; frequency ride-through settings; dynamic volt/var operations requirements; ramp rate requirements; fixed power factor requirements; and reconnection by soft-start methods.

California’s new standards draw from the European Union’s experience utilizing solar PV inverters to provide reactive power support. In Europe, advanced inverters have proven to be one of the most cost-effective improvements for reliability and efficiency of the power grid when paired with distributed generation. Similarly, delays in implementing advanced inverter functionality in some parts of Europe have lead to avoidable upgrades and some inverter retrofits. Proactive implementation of new standards for advanced inverters in the U.S. will accelerate the transition towards cost-effective local renewable energy generation.

Back-up power systems and replacement of existing inverters are exempted from California’s new requirement. California utilities will seek approval from the Federal Energy Regulatory Commission (FERC) as needed to harmonize federal interconnection standards with the revisions to California’s Rule 21.

The Smart Inverter Working Group and CPUC are now developing subsequent communication and control standards to realize the full potential of advanced inverters. Completion of these standards is expected in 2015 for adoption into the Rule 21.

Following this, the Working Group is tasked with establishing appropriate compensation to inverter owners for the provisioning of grid services.


John Bernhardt, Outreach & Communications Director
Clean Coalition
(703) 963-8750

About the Clean Coalition

The Clean Coalition is a nonprofit organization whose mission is to accelerate the transition to renewable energy and a modern grid through technical, policy, and project development expertise. For further information on the Clean Coalition, please visit

Craig Lewis

Founder and Executive Director

Craig founded the Clean Coalition in 2009 and has over 30 years of experience in policy and technology innovation, including the proliferation of Solar Microgrids and Community Microgrids. Prior to founding the Clean Coalition, Craig held numerous positions in the wireless, semiconductor, banking, and renewable energy industries. Previously VP of Government Relations at GreenVolts, he was the first to successfully navigate a solar project through California’s Renewable Portfolio Standard solicitation process. Craig was energy policy lead on Steve Westly’s 2006 California gubernatorial campaign. His resume includes senior government relations, corporate development, and marketing positions at leading wireless, semiconductor, and banking companies such as Qualcomm, Ericsson, and Barclays Bank. Craig received an MBA and MSEE from the University of Southern California and a BSEE from the University of California, Berkeley.