A microgrid is a localized energy system that can operate connected to the main grid or independently (islanded), combining distributed energy resources such as solar PV, battery energy storage, and backup generators with controllable loads like EV chargers. Microgrids use intelligent control to balance generation, storage, and demand within a defined site or campus.
What Is a Microgrid?
A microgrid is essentially a “small power system” serving a specific area, such as:
– A commercial site or industrial facility
– A campus (university, hospital, business park)
– A residential development or mixed-use district
– A logistics depot or port
It typically includes:
– Local generation (e.g., PV, CHP)
– Energy storage (battery systems)
– Loads (buildings, HVAC, process equipment, EV charging)
– Control and protection systems that manage power flows safely
A key feature is the ability to island, meaning the microgrid can disconnect from the utility grid and continue supplying selected loads.
Why Microgrids Matter for EV Charging
EV charging adds significant electrical demand and can increase maximum demand and grid connection costs. A microgrid can:
– Reduce peak import using storage and peak shaving
– Support more chargers without immediate grid upgrades by managing site capacity
– Improve resilience: keep critical charging running during outages (fleet readiness, emergency services)
– Increase renewable self-consumption by charging when PV output is high
– Enable advanced managed charging strategies tied to onsite energy availability
For fleets and campuses, microgrids help keep operations stable while electrifying transport.
How a Microgrid Works
– Monitors site demand and available local generation in real time
– Controls storage charge/discharge to balance supply and demand
– Coordinates controllable loads (including EV chargers) to respect a maximum site demand limit
– Manages import/export with the grid when connected
– If islanded, prioritizes critical loads and maintains voltage/frequency stability
Microgrid control is typically performed by an energy management controller that communicates with meters, inverters, and load controllers.
Grid-Connected vs Islanded Operation
Grid-connected mode
– The site remains connected to the utility grid
– The microgrid optimizes cost, carbon, and demand peaks
– Can export surplus energy (subject to connection rules)
Islanded mode
– The site disconnects from the grid during outages or planned islanding
– The microgrid supplies loads using local generation and storage
– Non-critical loads may be curtailed to preserve stability
Not all microgrids are designed for islanding; some are grid-connected only.
Microgrids and EV Charging Integration
Common integration approaches:
– EV charging as a controllable load using load balancing and dynamic load management
– Tariff- and PV-aware charging schedules (charge more when solar is abundant)
– Storage-assisted charging to reduce demand spikes and protect the main fuse rating
– Fleet charging priority rules (ensure vehicles are ready by departure time)
– Site-level metering via meter cabinets for monitoring, billing, and optimization
Key Benefits
– Improved energy resilience and business continuity
– Lower peak demand and potentially lower energy costs
– Better utilization of onsite renewables
– Increased hosting capacity for EV chargers on constrained sites
– More predictable site power performance under variable loads
Limitations to Consider
– Higher CAPEX and design complexity (controls, protection, storage)
– Regulatory and interconnection requirements can be strict
– Islanding requires careful protection coordination and controls
– Benefits depend on tariffs, load profile, and renewable/storage sizing
– Requires ongoing monitoring and maintenance to sustain performance
Related Glossary Terms
Managed charging
Load balancing
Dynamic load management
Maximum demand
Maximum site demand limit
Peak shaving
Energy management
Battery energy storage system (BESS)
Renewables integration
Main LV panels