What Are Distributed Energy Resources?

Distributed energy resources (DER) are electrical generation, storage, or load-management assets located at or near the point of consumption, connected to the distribution grid rather than to the high-voltage transmission system. The category encompasses solar photovoltaic arrays, small wind turbines, battery energy storage systems, fuel cells, combined heat-and-power units, and controllable loads such as electric vehicle chargers. Unlike large central generating stations, DER units are typically rated below 10 megawatts and often below 1 megawatt, and their aggregate behavior has grown significant enough to reshape the planning and operation of distribution networks.

The rapid adoption of rooftop solar and grid-scale battery storage has elevated DER from a marginal supply source to a central planning consideration for utilities. IEEE Standard 1547, which governs the interconnection and interoperability of DER with electric power systems, has been revised and expanded over successive editions to address the increasing capability of DER to participate in voltage regulation, frequency response, and reactive power support, functions previously reserved for large generators.

Types of Distributed Energy Resources

Solar photovoltaics represent the most widely deployed DER type, converting sunlight directly to direct current through semiconductor junctions; inverters then condition the output for grid injection. Battery storage systems, particularly lithium-ion chemistries, complement variable generation by storing excess energy and releasing it when generation falls or demand peaks. Fuel cells generate electricity through electrochemical reactions, producing heat as a byproduct that can be recovered in combined heat-and-power configurations for facilities requiring both electricity and thermal energy. Microturbines operate on natural gas or biogas and offer fast ramp rates, making them useful for peaking applications. Together, these technologies present utilities with both an opportunity to defer transmission investments and a challenge in managing the two-way power flows that DER creates on networks originally designed for one-directional delivery.

Grid Integration and Standards

Connecting DER to the grid requires meeting technical requirements for power quality, safety, and system stability. IEEE 1547 specifies performance thresholds for voltage ride-through, frequency ride-through, and islanding prevention, which stops DER from energizing a de-energized segment of the grid during a fault. The 2018 revision of the standard added provisions for active voltage support, allowing DER to inject or absorb reactive power on command from the distribution operator. Research published through NREL has examined the interaction between IEEE 1547 and IEEE 2030, the latter addressing smart grid communications, noting that interoperability between DER inverters and utility control systems is as important as the electrical performance specifications themselves.

Energy Management and Control

Aggregating DER into virtual power plants or microgrids requires control architectures that coordinate hundreds or thousands of individual assets. Centralized approaches rely on an energy management system that collects real-time data from each DER and dispatches setpoints, which works well for small fleets but does not scale to large numbers of endpoints with intermittent connectivity. Distributed control strategies, including droop control for frequency and voltage regulation, allow DER to respond autonomously to local signals without waiting for a central instruction. Advanced distribution management systems increasingly incorporate forecasting for solar and load, stochastic optimization under uncertainty, and demand response programs that adjust controllable loads to shift consumption away from peak periods.

Applications

Distributed energy resources have applications in a wide range of fields, including:

• Residential and commercial solar-plus-storage systems providing bill savings and backup power
• Microgrids at campuses, military installations, and remote communities operating independently during grid outages
• Electric vehicle managed charging programs using vehicle batteries as flexible grid assets
• Industrial facilities co-generating heat and power from fuel cells or microturbines
• Utility demand response programs aggregating building loads and batteries to provide ancillary services