The Energy Storage Report 2024

Now available to download, covering deployments, technology, policy and finance in the energy storage market

The long-awaited IEEE standard that paves the way for more energy storage on a smarter grid

By Brian Lydic

A newly released standard – IEEE 1547.1-2020 – creates nationally applicable guidance for distributed energy resource (DER) manufacturers on how grid support functions in their products will be tested. This paves the way for U.S. states to adopt more modern interconnection requirements for DERs on the grid, contributing to the grid modernisation that will be needed to support high levels of renewable energy and energy storage.

Brian Lydic is chief regulatory engineer at the Interstate Renewable Energy Council (IREC), a US-based organisation which aims to build the foundation for rapid adoption of clean energy and energy efficiency to benefit people, the economy and our planet. 

This article requires Premium SubscriptionBasic (FREE) Subscription

Enjoy 12 months of exclusive analysis

  • Regular insight and analysis of the industry’s biggest developments
  • In-depth interviews with the industry’s leading figures
  • Annual digital subscription to the PV Tech Power journal
  • Discounts on Solar Media’s portfolio of events, in-person and virtual

Or continue reading this article for free

As the grid evolves and more distributed energy resources (DERs), like solar and energy storage, are added, the dynamics of the grid are becoming more complex. As we look towards a future where renewable energy supplies a large proportion of electricity, new “grid support” functionality in DERs (including inverters) will be important to help ensure that the grid functions reliably. 

In recent years, some U.S. states have begun to require that inverters with these functions (“smart inverters”) be used when connecting DERs to the grid (“interconnection”). Smart inverters can “see” information about the grid at their location (i.e. voltage and frequency) and can respond autonomously in ways that help maintain grid stability. However, to date there have been no test procedures that hardware manufacturers could look to for guidance on how smart inverters could comply with a national standard, complicating the process of bringing compliant products to market. 

A newly released, but long-awaited, standard from the Institute of Electrical and Electronics Engineers (IEEE)—Standard 1547.1™-2020—establishes these testing procedures. This gives much needed certainty to manufacturers so they can create products they know will be compliant with requirements that are now being put in place by leading states adopting new national standards. 

It also paves the way for more states to require grid support functionality for DERs connecting to the grid, because they can be confident that compliant products will soon be readily available. In this way, the release of IEEE 1547.1-2020, will contribute to progress on the grid modernisation efforts needed to support high levels of DERs including energy storage. 

In this article, I explore the significance of the IEEE 1547.1-2020, the timeline for its implementation, and the status of state-level adoption of modern DER interconnection requirements enabled by this new development.

A major milestone for adoption of improved DER interconnection rules

In April 2018, IEEE published “base standard” IEEE Standard 1547™-2018, which laid out many sweeping changes to the technical rules of interconnection for DERs, compared to the previous version from 2003. The capabilities of modern equipment connecting to the grid had advanced substantially, especially for smart inverters which were adapting to higher penetration around the world, and IEEE 1547-2018 modernised interconnection requirements to reflect the need for these capabilities. 

However, the test procedures for dealing with those new capabilities needed major revision before any equipment could be certified for the new standard. Product engineers typically rely to a large extent on the test procedures during the design phase to ensure the product they are building will pass the tests once the design is finalized. 

On May 21, 2020, the Institute of Electrical and Electronics Engineers (IEEE) published IEEE Standard 1547.1-2020, IEEE Standard Conformance Test Procedures for Equipment Interconnecting Distributed Energy Resources with Electric Power Systems and Associated Interfaces. This is the test standard for grid interaction for solar PV and battery storage inverters, as well as other DERs, based on the requirements of IEEE 1547-2018. That day had been long anticipated by states and utilities preparing to implement advanced or smart inverters (or doing so already). 

Now that IEEE 1547.1-2020 is published, inverter and other equipment manufacturers can re-engineer existing products as needed, or design new ones to meet the requirements of IEEE 1547-2018. There is also now greater certainty for states and utilities working to adopt IEEE 1547-2018 because they have a clearer timeline for when they can expect certified products on the market.

Paving the way for grid modernisation

Today, most U.S. states and utilities have yet to adopt DER interconnection requirements based on IEEE 1547-2018; most continue to use requirements based on the 2003 version. One reason for this is that it would be challenging to implement the new standard without certified compliant products (e.g. PV or storage inverters) on the market. Now, with the publication of IEEE 1547.1-2020, states and other stakeholders have a clearer picture of when they are likely to be available. This will help those working to adopt the new standard understand when it can actually be implemented. 

PV and storage inverters and some other products are listed to the safety standard UL 1741, which requires grid interactive equipment to pass the tests in IEEE 1547.1. UL is preparing to publish updates to this standard in early August to reference the new tests in the 2020 version. After that, manufacturers will be able to certify inverters to the requirements of IEEE 1547-2018. 

Note that in the past, updates to UL 1741 (the “Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use with Distributed Energy Resources”) have been given a grandfather period, typically 18 months, during which either the older or newer requirements may be used for product certification. This gives the manufacturers time to develop the products to meet the new requirements. However, this is the first time IEEE Standard 1547™ has been revised, and with such major changes it is unclear how it will be adopted throughout the nation. For the time being, UL 1741 will leave the grandfather period open-ended and allow the manufacturer to certify to either the 2003 or 2018 requirements. Over time, once it is clear that most jurisdictions require the 2018 version of the standard, UL 1741 will be updated again to remove any reference to the old standard and manufacturers will have to meet the requirements of IEEE 1547-2018 moving forward.

Although UL will provide a grandfather period in which manufacturers may continue to use the older testing requirements for product certification, we may see products certified to the new standard before the end of 2020, with more coming to market in 2021 to meet requirements already in place in leading states. 

It should be noted that UL has a supplement (UL 1741 Supplement SA) that defines some test procedures for advanced inverter functions similar to those now required by IEEE 1547-2018. These test procedures have been used by California, Hawaii and some other locations for certification of inverters since September 2017, in advance of IEEE’s new standards being developed. IEEE 1547.1-2020 supplants most of the tests in Supplement SA, so inverters will not need to be tested to both sets of procedures. Most or all of the supplement will be removed from UL 1741 after the grandfather period has closed.

As the grid evolves and more distributed energy resources (DERs), like solar and energy storage, are added, the dynamics of the grid are becoming more complex. Image: 8minute Solar Energy.

Maryland and Hawaii: The Race Is on for Compliant Products

Maryland updated its interconnection rules (Code of Maryland Regulations 20.50.09) this year with a requirement that DER systems must utilise inverters certified to IEEE 1547-2018 in order to be approved for interconnection to the grid starting January 1, 2022. 

The Hawaiian utility Hawaiian Electric already required advanced inverters tested to UL 1741 Supplement SA, and has been working to harmonise its interconnection (Rule 14H) requirements with the new IEEE standard. They recently released inverter capability requirements, noting those which differ from IEEE 1547-2018 for frequency support due to the island nature of Hawaii’s electric system (Source Requirements Document Version 2.0). Those requirements, in addition to the rest of IEEE 1547-2018, must be met for interconnections beginning January 1, 2022 as well. 3 

This gives manufacturers about 19 months from the publication of IEEE 1547.1-2020 to be certified for those markets. This may be just enough time for many products to be certified.


April 2018 IEEE publishes 1547-2018
May 2020 IEEE publishes 1547 .1-2020
August 2020 UL updates 1741 allowing start of DER testing and certification
2021-2022 Tested and certified 1547-2018-compliant DER available on market

Adoption around the States

Minnesota was the first state to undertake the significant lift of modernising its technical interconnection rules to reflect advanced grid support functionality now reflected in IEEE 1547-2018, helping to ensure that high levels of DERs can be integrated without adverse effects on the grid. Minnesota both created technical interconnection rules from scratch and adopted IEEE 1547-2018 in the process (State of Minnesota Technical Interconnection and Interoperability Requirements, or TIIR).

However, the state opted to wait to order implementation of elements of the TIIR that require IEEE 1547-2018 certified equipment until a later date when it is clear that such equipment is readily available on the market. This perfectly illustrates the significance of IEEE 1547.1-2020 in enabling states to move forward with modernising their interconnection requirements to enable a smarter grid with more renewables and energy storage. 

Massachusetts utilities are currently at work developing proposals for adopting the interconnection requirements established in IEEE 1547-2018. This work is being led by a task force as part of their Technical Standards Review Group (TSRG). It is envisioned that the proposals will develop into revisions to the TSRG’s Common Technical Standards Manual, but no specific date is yet targeted for implementation. 

California is just beginning its efforts to harmonise its interconnection requirements (Rule 21) with IEEE 1547-2018. Since Rule 21 already contains advanced inverter requirements, California’s Smart Inverter Working Group (which helped create the requirements) will convene to determine how to revise Rule 21 and transition to utilizing IEEE 1547-2018. It is anticipated that revisions to Rule 21 will be submitted to the California Public Utilities Commission in February 2021. Determining the implementation date for the new requirements will be part of that process. 

Now that a fully developed national standard exists (IEEE 1547-2018, paired with the testing procedures in IEEE 1547.1-2020), there is a standard that all states can adopt. This means that individual states will no longer have to undertake the arduous process of developing their own requirements, as California did. The national standard has caught up to where forward-looking states were heading on their own.

Looking forward

Now that equipment certification for IEEE 1547-2018 requirements is available through IEEE 1547.1-2020, the stage is set for more states and utilities to adopt these modernised interconnection requirements that will enable greater DER deployment in the long term. The publication of IEEE 1547.1-2020 provides greater clarity on the realistic timeline for implementation. Over the next year or so we will get a better picture of the developing market for products certified to the new standard. 

The National Association of Regulatory Utility Commissioners adopted a resolution [2] recommending that states “adopt the current IEEE 1547; and align implementation of the standard with the availability of certified equipment.” If states were waiting for a “starting gun” for beginning the adoption and implementation of the new standard, the publication of IEEE 1547.1-2020 is exactly that.


Notes: [1] More information about Hawaii’s implementation of IEEE 1547-2018 can be found on Hawaiian Electric’s Customer Energy Resource (CER) Equipment page.

[2] Resolution recommending state commissions act to adopt and implement DER standard IEEE 1547-2018


Cover Image Credit: GlidePath. 

Email Newsletter