About Microgrids

High-Level Microgrid Schematic
CERTS Microgrid Schematic

A microgrid is a localized group of electricity sources and sinks (loads) that typically operates connected to and synchronous with the traditional centralized grid (macrogrid), but can disconnect and maintain operation autonomously as physical and/or economic conditions dictate.

According to the U.S. Department of Energy Microgrid Exchange Group, the following criteria defines a microgrid:

A microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.

Additional information on microgrid definitions can be found at building-microgrid.lbl.gov/microgrid-definitions. Note there is no reference to the actual generation or other DER technologies involved, and in fact, many microgrids will involve a combination of resources, sometimes a quite complex one. There is also no specific guidance on the size of microgrids. Instead, microgrid definitions focus primarily on two features:

  • a microgrid is a locally controlled system
  • a microgrid can function both connected to the traditional grid (megagrid) or as an electrical island.

There are two major types of microgrids, as discussed in building-microgrid.lbl.gov/types-microgrids. These include microgrids wholly on one site, akin to a traditional utility customer, which are usually called customer microgrids or true microgrids (µgrids), and microgrids that involve a segment of the legacy regulated grid, often called milligrids (mgrids).

The operation of microgrids offers distinct advantages to customers and utilities, i.e. improved energy efficiency, minimization of overall energy consumption, reduced environmental impact, improvement of reliability of supply, network operational benefits such as loss reduction, congestion relief, voltage control, or security of supply and more cost efficient electricity infrastructure replacement. There is also a philosophical aspect, rooted in the belief that locally controlled systems are more likely to make wise balanced choices, such as between investments in efficiency and supply technologies. Microgrids can coordinate all these assets and present them to the megagrid in a manner and at a scale that is consistent with current grid operations, thereby avoiding major new investments that are needed to integrate emerging decentralized resources. Microgrids have been proposed as a novel distribution network architecture within the SmartGrids concept, capable to exploit the full benefits from the integration of large numbers of small scale distributed energy resources into low-voltage electricity distribution systems.

At the highest level, the SmartGrid has 3 components:

  • improved operation of the legacy high voltage grid, e.g. through use of synchrophasers
  • enhanced grid-customer interaction, e.g. by smart metering or real-time pricing
  • new distributed entities that have not existed previously, e.g. microgrids and active distribution networks.

Some examples of microgrids can be found at building-microgrid.lbl.gov/examples-microgrids
Occasionally, news relevant to the microgrid group at Berkeley Lab can also be found at building-microgrid.lbl.gov/news


The microgrids team at Berkeley Lab actively publishes the results of its research in peer-reviewed journals. Examples include the study of microgrid value streams, modeling microgrid participation in ancillary service markets, stochastic variability of solar irradiance in microgrid design, or advanced modeling methods used to obtain resilient security-constrained microgrid designs.

All our microgrid related publications can be found at building-microgrid.lbl.gov/publications