The Integrated Grid: How Do We Get There?


EPRI’s roadmap for distributed energy.

Fortnightly Magazine - June 2015

In 2014 we published a paper at the Electric Power Research Institute (EPRI) to introduce our concept of The Integrated Grid, a cost-benefit framework that will focus on the widespread deployment of distributed energy resources (DERs). At that time rooftop solar stood front and center as a bellwether technology - creating a new type of grid that differs fundamentally from the one dating to the formative years of Edison and Westinghouse.

Many groups and individuals have offered their visions and pragmatic observations about how this new 21st Century grid will operate when it fully integrates thousands of rooftop solar panels, residential battery packs, and perhaps millions of battery-driven cars and trucks that will alternately draw power and yet also feed it back into the system. Sensors and digital technologies will join the mix - some from familiar technology companies, and perhaps others from app shops in some tinkerer's garage. Microgrids also may emerge, to compete for customers across today's familiar residential, commercial, and industrial landscapes.

To realize the full value of these distributed resources, while continuing to provide electricity affordably and reliably, we must integrate DER into every aspect of grid planning, operations, and policy. Failure to do that could drive up costs and drive down reliability. And so, as we plan for these new technologies, configurations, and systems, we should lay the groundwork for the future - for technologies and applications that today we can sketch out only crudely.

(For more information about EPRI's Integrated Grid Initiative, and the Integrated Grid: A Benefit-Cost Framework Report, visit

At EPRI we have a sense of urgency to move from crude sketches to sharp pictures. We are joining with people in utilities, regulatory bodies, stakeholder groups, and various customer groups in bringing both optimism and pragmatic questions about what The Integrated Grid means. And we do this for one very good reason: Today's grid works exceedingly well for billions of people and does so at a very good price. We'd like to keep it that way.

Mapping the Transition

Figure 1 - EPRI’s Integrated Grid Benefit/Cost Framework

Which technological improvements and policy incentives can best drive our changing industry? How do we identify and enable the best consumer choices as they expand to include?

  • Generation. Owning or leasing distributed generating systems, such as photovoltaic (PV) solar, thermal, wind, and biomass);
  • Storage. Using storage options and technology to manage costs; and
  • Micro vs. Macro. Integrating technologies on the customer side (systems, monitoring, control, and communication) with those under the control of system operators on the grid-side.

At this stage, utilities remain sharply focused on how to ensure that existing assets perform effectively while adapting to a changing grid, and while creating and deploying new technologies. At EPRI we share this focus. Yet we see much work ahead in key technical and operational areas.

We need to identify optimal architectures and the most promising configurations, recognizing that solutions vary with local circumstances, goals, and interconnections. We must look methodically at the ways in which diverse distributed resources interact with the power system infrastructure. Beneficial and adverse circumstances can arise at differing levels of DER penetration, and will depend on specific characteristics of a given distribution circuit, including its design, equipment, and the variation over time of its loads, generation, environmental conditions, and other factors.

Like politics, the dynamics of individual circuits is about to become very local. Customers may rely on Hawaiian sunlight, Dakota winds, or Oregon rainfall, and they may enjoy similar opportunities and benefits from these distributed resources, but the particulars of their situations - the systems, technologies, regulations, and markets - will be markedly different. And so it becomes critical to take systematic steps to understand and map each transition.

For this reason, benefits and costs must be understood and characterized at the local level, but then extended and aggregated at the level of the overall power grid. For this task, EPRI is proposing two broad phases of work: (a) The Integrated Grid Benefit-Cost Framework and (b) its associated groups of pilot projects.

Benefits and Costs

At this year's NARUC Winter Meeting, EPRI released what we call the Integrated Grid Benefit-Cost Framework to guide utilities and regulators in a complete analysis of how to optimally integrate DERs with central generation and grid operations.

EPRI's benefit-cost framework employs available power system and economic models, methods, and data to construct a complete, end-to-end portrayal of how distributed resources impact the electric system, and how to understand those impacts in terms of cost and benefits to society.

We are engaging with utilities and regulators to apply the framework in different jurisdictions and operating environments. By doing this we can move toward a more precise understanding of this grid-transforming process and a broader understanding of how it will need to be carried out, given the diversity of utility asset portfolios and operating conditions. EPRI's benefit-cost methodology defines the tools, protocols, and methods necessary to conduct consistent, repeatable, and transparent studies to anticipate and accommodate DER. By rooting it in power system engineering and economics, we have designed it to apply to all regions, systems, markets, technologies, and research questions.

EES North America

And this universality is important. By applying our framework across diverse systems and operating conditions, we aim for coherence, consistency, and accuracy - to give utilities and other stakeholders the ability to compare and contrast studies and make the results understandable and applicable to others. Ultimately we seek a comprehensive understanding of the impacts when distribution systems of differing designs and demand profiles, markets will choose to integrate DERs at low and high levels.

Our Integrated Grid Benefit-Cost Framework (see also, Figure 1) contains four analytic elements:

  1. Core Assumptions.
  2. Distribution System Impacts.
  3. Bulk Power System Impacts.
  4. Benefit-Cost Analysis.

Core Assumptions. First, we specify market conditions, DER adoption, and define scenarios. We then use these data to identify and quantify the impacts of DER on the distribution system and on the bulk power system.

Distribution System Impacts. Second, we identify and quantify distribution system impacts attributed to interconnected DER, and then determine the level of DER interconnection that can be accommodated locally without impacting the quality of supply for the existing infrastructure. Energy, capacity, and reliability analyses are used to identify designs and approaches that take advantage of the DER benefits while avoiding adverse impacts.

Bulk Power System Impacts. Third, we address resource adequacy, making sure that sufficient resources are available to meet electricity demand. Then we determine whether the power generated can be delivered to the distribution system without a drop in service reliability (including the benefits and impacts of distributed resources). After that, we conduct analyses of transmission performance, system flexibility, and operations practices and simulation to consider all system benefits and impacts.

Benefit-Cost Analysis. In the fourth step, we process the aggregate impacts and measure net benefits. This element anticipates the use of a reference case for comparing DER interconnection cases. The reference case may omit or include DERs connected only at the time of the study. Alternatively, the study may stipulate a level (or levels) of DER adoption and determine the resulting impacts. Either approach points to the implications of different levels of DER adoption on distribution circuits, as well as different approaches for related system design modifications.

In the distribution and bulk power system analyses, many of the impacts identified relate to costs incurred (to mitigate adverse impacts, for example) or to costs saved - those that otherwise would be incurred but are avoided. Other impacts define changes in the system that are tangible and should be identified and quantified but not in monetary terms. Such "externalities" can include emissions, changes in delivery reliability, and in the affected economy (such as employment and wages).

Assessing benefits and costs in monetary terms to the greatest extent possible can better reflect the net benefits to the utility, its customers, other economic sectors and society as a whole. The framework proposes alternatives for doing this.

In his March 19 blog, Natural Resources Defense Council Policy Analyst Pierre Bull characterized the framework as "highly technical" and instructed his readers to consider the document " … a kind of pleasure reading for grid operators, electrical engineers and policy wonks." (See, "A New Tool to Assess the Benefits and Costs of Distributed energy Resources from the Electric Power Research Institute," at

Bull concludes the blog by writing, "EPRI should be commended for making it possible for utilities, regulators, environmentalists, consumer advocates and policymakers to work from a common framework and speak a common language, with The Integrated Grid."

I'll acknowledge as both engineer and policy wonk that I consider the framework a good read, a common framework, and the basis for a common language. But more important, it is a real tool to do real work. At EPRI we are keen to see this tool put to the test.

And we won't forget the human angle. At EPRI, we see important work ahead in better understanding what customers want and need, along with specifics of when and how they use electricity. After all, it's the customer who likely will decide what hardware to buy. Their purchasing decisions will soon have much broader and deeper effects on the grid than the old days, when a small decision was whether to buy a two-slice or a four-slice toaster and a big decision was whether to cook with gas or electricity. We must know what will drive people to adopt DER and be able to forecast how electricity demand changes as a result. Beyond this we must work toward forecasting how much and what kinds of DER are likely to be interconnected.

Pilot Projects

For EPRI, deploying the framework is the first step, and one that, as I have indicated, we are eager to see deployed by a variety of utilities. At the same time, however, the technologies and operating procedures that will equip The Integrated Grid to supplant its traditional predecessor must be subjected also to rigorous, in situ field testing. To that end, we at EPRI have identified five areas at this stage, pertaining to various technologies attached or integrated with the distribution system, in which coordinated pilot projects implemented by utilities and others can achieve material progress in advancing The Integrated Grid:

  • Utility-Scale PV;
  • Distributed Storage Systems;
  • Microgrids;
  • EV Charging Infrastructure; and
  • Customer-Side Technologies.

Utility-Scale PV. Whether with or without storage, utility-scale PV can be centrally controlled and dispatched, and yet attached to the distribution system. In this area, pilot projects are needed to confirm the level and timing of the output of the PV system and to ensure that interconnection and grid coordination systems operate as designed - and that the design itself achieves effective integration. We see the need to verify the performance of coordinated storage systems in a production environment. We also need to verify strategies for maximizing the value of PV and storage, and identify and resolve any performance deficiencies.

Distributed Storage Systems. Here, field tests are needed for customer-side distributed storage systems that are operated in conjunction with intermittent DERs to confirm that storage coordination strategies based on simulations can in fact provide benefit to customers and the grid, when operated on the customer premises.

Microgrids. Electric service reliability and resiliency can be improved with microgrids. And we understand also that microgrids can serve as a system support asset. Yet the benefits are speculative until confirmed in practical applications in which systems are fully interconnected with - and operated in coordination with - the grid.

EV Charging Infrastructure. At present the potential extent and frequency of EV charging infrastructure is a matter of conjecture, and therefore so too are the grid impacts and benefits. Pilot projects for the operation of at-scale facilities can help determine how the system is impacted, verify operating strategies, and inform refinements.

Customer-Side Technologies. Lastly, we would like to see pilot projects for customer-side technologies that produce, store, and manage electricity. Here, the relatively high rate of PV adoption in some areas provides an apt testing ground to resolve both technical and behavioral questions regarding the effects of DERs on the electric system.

For all of these pilot projects, we will promote and support ongoing technology assessments and performance documentation in conjunction with other stakeholders and will work with utilities globally to coordinate system pilots, deployment, and modeling that contribute to the effective integration of DER. We will engage also with the National Association of Regulatory Utility Commissioners, Institute of Electrical and Electronics Engineers, International Council on Large Electric Systems, and the U.S. Department of Energy and its network of national laboratories, national electricity trade associations {including Edison Electric Institute , the National Rural Electric Cooperative Association, the American Public Power Association and other organizations to both apply and hone the Integrated Grid Benefit-Cost Framework.

These pilot projects will help provide the data and experience that take us to the next step, which may include more widespread adoption and faster progress. I expect that we can see in a relatively short time, consumers buying and relying on devices that manage their supply and use of electricity in new ways - and in ways that advance their individual interests along with those of the grid and the people around them.

The engineer in me is eager to see the rigorous studies and work that we need to quantify the benefits and the costs of The Integrated Grid. And as a leader of the EPRI team, I am eager to see new opportunities and new benefits emerge for all of us who rely on electricity.