DER Participation in Electricity Markets

1. Introduction

DERs (Distributed Energy Resources) are small energy resources located close to consumers. Examples include rooftop solar, batteries, electric vehicles, small wind turbines, combined heat and power units, heat pumps and flexible electricity demand.

Traditionally, electricity markets were designed mainly for large power stations. DER participation changes this model because thousands of small resources can now produce electricity, store it, reduce consumption and provide flexibility.

Therefore, DER participation in electricity markets means giving these small resources appropriate legal and commercial opportunities to participate in electricity generation, supply, balancing, flexibility and capacity markets.

Ofgem has recognised that direct market access for independent aggregators can create consumer benefits, while also identifying the need for proper rules concerning access, measurement, pricing, balancing responsibility and delivery risk. (Ofgem)

2. Meaning of DER Participation

DER participation can happen in several ways:

Generation – rooftop solar or small generators sell electricity.

Storage – batteries charge when electricity is cheap and discharge when needed.

Demand response – consumers reduce or shift consumption.

Flexibility services – DERs respond to network or system requirements.

Capacity markets – aggregated resources provide capacity during periods of system stress.

Balancing markets – DERs help maintain real-time supply-demand balance.

Thus, DERs are becoming both consumers and active market participants.

3. Role of Aggregators

A major problem is that one household battery or solar installation may be too small to participate directly.

An aggregator solves this problem by combining many small resources.

For example:

500 batteries + 300 EVs + 200 solar systems → Aggregator → Electricity market

The aggregator can offer the combined capacity as one market resource.

Ofgem has specifically supported the idea of independent aggregators accessing additional electricity markets, subject to appropriate market design. (Ofgem)

This is important because aggregation allows small consumers to participate without individually meeting all the technical and administrative requirements of large generators.

4. Access to Electricity Markets

A central legal issue is equal and fair market access.

Traditional market rules can create barriers because they were designed for large generators.

For example, a small battery may face requirements concerning:

minimum capacity;

metering;

registration;

forecasting;

balancing responsibility;

technical performance; and

settlement.

If these requirements are unnecessarily difficult, DER participation becomes practically impossible.

Therefore, regulation increasingly tries to make requirements proportionate to the size and function of the resource.

5. Demand-Side Participation

DER participation is not limited to electricity generation.

Consumers can also participate by changing their electricity consumption.

For example:

an EV can charge later;

a battery can stop charging during system stress;

a heat pump can temporarily change its consumption;

an industrial consumer can reduce demand.

This is called demand-side response (DSR).

Ofgem has identified demand-side participation and aggregation as important mechanisms for improving flexibility in electricity markets. (Ofgem)

6. DERs and Balancing Markets

Electricity supply and demand must remain balanced.

DERs can help by:

increasing generation;

reducing demand;

discharging batteries;

delaying electricity consumption; or

changing charging patterns.

This makes DERs useful for balancing the electricity system.

The legal framework must establish:

who can submit bids;

how flexibility is measured;

who is responsible for non-delivery;

how participants are paid; and

how imbalance costs are allocated.

These questions become especially important when an aggregator controls thousands of separate devices.

7. DERs and Capacity Markets

DERs can also participate in capacity markets, where participants receive payments for being available when the electricity system needs additional capacity.

Aggregation is particularly important because individual small resources may not satisfy minimum capacity requirements.

Ofgem has previously noted that aggregators can allow individual demand-side resources that would otherwise be too small to participate in the Capacity Market. (Ofgem)

This creates a legal connection between small-scale resources and national electricity-security policy.

8. Important Regulatory Development: BSC Modification P455

A good example of regulatory reform is BSC Modification P455, approved by Ofgem in September 2024.

The modification introduced an on-site aggregation methodology to facilitate third-party access for domestic and small-business consumers located on microgrids or private networks.

Ofgem noted that although such consumers had a legal right to switch suppliers, existing industry procedures were not suitable for many of these customers. (Ofgem)

Relevance

This demonstrates that market participation is not only about producing electricity. It also requires settlement, metering and switching arrangements that allow smaller consumers to participate effectively.

9. Measurement and Settlement

Accurate measurement is essential.

Suppose an EV normally consumes 10 kWh but consumes only 6 kWh after an aggregator sends a flexibility signal.

The market needs to establish whether the 4 kWh difference was actually delivered flexibility.

Therefore, regulators need:

accurate meters;

reliable data;

baseline methodologies;

settlement rules; and

verification procedures.

Without accurate measurement, DER participation could result in incorrect payments or unfair allocation of balancing costs.

Ofgem has specifically identified measurement and balancing responsibility as important issues in designing aggregator access. (Ofgem)

10. Case Law: R (SSE Generation Ltd) v CMA

In R (SSE Generation Ltd) v Competition and Markets Authority [2022] EWCA Civ 1472, the Court of Appeal considered the operation of the electricity balancing arrangements.

The case concerned the Balancing and Settlement Code and the operation of the balancing mechanism.

Relevance to DERs

Although the case was not specifically about household DERs, it demonstrates the importance of the BSC as a legal and commercial framework for electricity-system balancing.

As DERs increasingly participate in balancing markets, their activities must fit within these established settlement and balancing arrangements.

11. Case Law: PreussenElektra AG v Schleswag AG

The EU Court of Justice decision in Case C-379/98, PreussenElektra AG v Schleswag AG concerned German legislation requiring electricity suppliers to purchase electricity generated from renewable sources at minimum prices.

The Court held that the particular purchasing obligation did not constitute State aid because of the way the scheme was financed. (Court of Justice of the European Union)

Relevance

The case demonstrates how governments can legally create market-access mechanisms for small and renewable electricity producers while pursuing broader energy-policy objectives.

It is particularly relevant to the development of decentralised renewable generation.

12. Competition and Non-Discrimination

DER participation also raises competition questions.

Large generators and small distributed resources should not face unjustified discriminatory treatment.

However, technical requirements can legitimately differ where resources have different physical characteristics.

For example, a 1 MW battery and a 1,000 MW power station may reasonably have different technical obligations.

The legal principle should therefore be proportionate and technology-neutral regulation, rather than identical treatment in every situation.

13. Local and National Markets

DERs can provide services at two different levels.

Local level

A distribution network may need flexibility to manage:

congestion;

voltage problems; or

local demand peaks.

National level

The national system operator may need resources for:

balancing;

frequency management;

capacity adequacy; or

system security.

This creates a need for coordination between local and national markets.

Ofgem appointed Elexon as the market-facilitator delivery body to help create more accessible, transparent and coordinated flexibility markets. (Ofgem)

14. Consumer Protection

DER participation must also protect ordinary consumers.

Important protections include:

informed consent;

transparent contracts;

clear payment arrangements;

protection of personal data;

cybersecurity;

safe remote control;

clear exit rights; and

protection from unexpected charges.

For example, if an aggregator remotely controls a household battery, the consumer should understand when it may be charged or discharged and how the consumer will benefit.

Therefore, DER participation is both a technical and consumer-law issue.

15. Future Importance

DER participation will become more important as electricity systems develop:

smart meters;

electric vehicles;

vehicle-to-grid systems;

home batteries;

community energy;

virtual power plants;

smart heat pumps; and

automated demand response.

Ofgem's recent market-facilitator framework recognises that the transition to renewable electricity requires greater flexibility and better coordination of local and national flexibility markets. (Ofgem)

16. Conclusion

DER participation in electricity markets represents a major change from the traditional centralised electricity model.

The important legal elements are:

Open and fair market access

Aggregation of small resources

Demand-side participation

Balancing-market access

Capacity-market participation

Accurate metering and settlement

Fair competition

Consumer protection

Coordination between local and national markets

Clear regulatory responsibility

The cases SSE Generation v CMA and PreussenElektra v Schleswag provide useful legal principles concerning electricity-market operation and renewable-generation access. Recent Ofgem reforms such as P455 show how the regulatory framework is being adapted to make participation easier for domestic and small-business resources. (Ofgem)

In simple terms, DER participation means changing consumers from passive users of electricity into active participants who can generate, store, reduce, shift and sell electricity. The legal challenge is to provide this participation while maintaining system reliability, fair competition, accurate settlement and consumer protection.