MISO's Missing Inventory: Why State Commissions Should Mandate a DER Registry.

Maryland PSC approved DER Registry concept just this week.

Distributed energy resources are growing across the MISO footprint, but there is no standardized, publicly accessible inventory of what exists, where, and whether it is participating in wholesale markets. Utilities have internal tracking systems but no incentive to share them. MISO focuses on operational dispatch, not transparency. The result is that regulators, developers, and advocates are making resource planning decisions with incomplete information. A DER Registry — housing both registered and unregistered DERs — would close that visibility gap and help state commissions finally answer the Virtual Power Plant potential question. The only realistic path to getting one built is a state commission mandate.

If we build it, will they come?

The primary question is straightforward: if we build a DER Registry, will DERs actually come? I can see the benefit from small DER owners’ perspective. It will give them access to a database that shows the number of DERs, the type of DER technology, where they are physically located, in which distribution utility and what their operational capabilities are.

A large DER owner or a market participant with years of experience operating in the wholesale market may not necessarily see the benefits of a DER Registry because they have internal databases and experiences that may be proprietary and a DER Registry would become one more layer of administrative burden for them.

Now, if we move to the concept of a DER Registry – a DER Registry in my mind would house all registered and un-registered DERs in the wholesale market. This will help interested stakeholders and policy makers address the barriers for each separately – why are unregistered DERs not registered with the market operator? What are the barriers for market registration? Versus, are the registered DERs participating in energy, capacity and ancillary services markets or just one of the markets? What are the barriers for the registered DERs?

We can all agree that we need more DERs in the wholesale marketplace to reduce consumer costs and for that to happen we need more DERs registered in the wholesale market. There is no way around this simple concept.

More DERs in the wholesale market means there is a need for something like a DER Registry because there is no generator interconnection queue like transparent DER listing on an Independent System Operator (ISO) website – they wouldn’t have one because DERs are primarily located on the distribution system not on the transmission system.

Some utilities won’t like it.

The biggest opposition for a DER Registry comes from distribution utilities because they might have their own internal DER Registry like databases that keep track of customer interactions right from the DER/DG interconnection phase to in-service date.

Distribution utilities typically track their customers in different classes based on the rates they charge them. A DER Registry is not necessarily asking them how many customers are taking a service in which class. A DER Registry would help them see the potential for Virtual Power Plant (VPP) MW capacity in an Integrated Resource Plan (IRP) proceeding. The answer to the VPP potential question would help the state regulators address the barriers to wholesale market participation for retail programs.

Hence, even though there is very little benefit for large utilities that have their own database to track DERs, a state commission should mandate a DER Registry to get to the heart of this VPP question. Otherwise, we are constantly facing this dilemma of how much generation is needed to serve load reliably in one IRP or distribution planning or rate case at a time.

Bigger problems for DERs remain.

The DER Registry will not solve all the barriers DERs have today. Even with FERC Order 2222 that allows aggregation of multiple DER technologies to participate in the wholesale marketplace, there are still multiple barriers to DER adoption like metering barriers that companies like Mission:data are on the front lines.

Most states have Integrated Distribution Planning dockets as well to integrate the generation and distribution planning but there is very little “integration” – generation is planned in an IRP and distribution system is planned in an IDP. State regulators have yet to standardize smart inverters across the board, mandate distribution utilities to provide real-time hosting capacity maps that benefit DER developers, and probe why there is a lack of non-wire alternatives in distribution system planning. But for those DERs that manage to pass through all these barriers, a DER Registry makes sense because stakeholders would need to track them in a wholesale market.

The answer is a mandate, not a request

A DER Registry will not emerge organically. Large utilities have no incentive to build one beyond their own internal tracking systems, and the stakeholders who would benefit most — small DER owners, aggregators, and ultimately ratepayers — don’t have the leverage to make it happen on their own.

A market operator like MISO is unlikely to provide a DER Registry like tool because they are more concerned with operational capabilities of DERs and ensuring the control room operators have access to DERs during emergency events. The operators are more concerned about the notification time – the lead time (6 hours or 30 mins) to call upon a DER, can they perform for 4 hours at a stretch, will they inject or reduce, where they are located etc.

That leaves state commissions. A commission mandate is the only realistic path to a DER Registry that is comprehensive, standardized, and actually useful for IRP and distribution planning proceedings. Without it, we will continue answering the VPP potential question one proceeding at a time, with incomplete data and no common framework. That argument no longer needs to be theoretical.

Maryland answers the question

As this post was being finalized, the Maryland Public Service Commission issued Order No. 92398 (May 6, 2026) in Case No. 9778 — and did exactly what this post argues is necessary. The Commission created a Data Exchange Work Group (DEWG) directed to file a DER Registry Roadmap within six months, comparing the costs of a centralized public-facing registry against standardized EDC-by-EDC registries. The Exelon Utilities and Potomac Edison must begin filing quarterly confidential DER registration reports within 90 days. And critically, the Commission set a hard deadline: Maryland-licensed DER Aggregators shall have access to all PJM-required DER information held by the EDCs by January 1, 2028 — regardless of whether the final registry architecture is centralized or utility-by-utility. The Maryland order is in PJM territory, but the logic is RTO-agnostic — and MISO states are watching.

The Commission also created a Green Button Connect My Data-compliant data exchange platform process — the infrastructure layer that the DER Registry will eventually sit on top of. Maryland didn’t just endorse the concept. It set deadlines, assigned accountability, and linked the registry to a live DERA access date tied to PJM’s own Order 2222 implementation schedule. Maryland’s order is a mandate to build the roadmap, not yet the registry itself — but the January 2028 DERA access deadline means the underlying infrastructure must be in place regardless of what form the final registry takes.

The barriers to DER participation in wholesale markets are real and layered — metering, interconnection, aggregation rules, smart inverter standards. A DER Registry won’t dissolve those barriers overnight. But you cannot systematically address what you cannot systematically see. A mandatory registry gives regulators, advocates, and developers a shared factual foundation to work from.

State commissions have both the authority and the obligation to close this visibility gap. The question is no longer whether a DER Registry makes sense. Maryland just answered which commission acts first. The question now is which commission acts second.