Grid-Forming vs. Grid-Following Inverters: What’s the Difference?

Grid-forming vs grid-following inverters is becoming an increasingly important distinction as batteries, solar arrays and other inverter-based resources make up a larger share of modern power systems.

Both types of controls use power electronics to connect energy resources with an AC electrical system. The fundamental difference is how they interact with that system.

A conventional grid-following inverter synchronizes with an electrical waveform that already exists. A grid-forming inverter can establish or regulate voltage and frequency rather than depending entirely on an outside waveform to tell it what to follow.

That difference becomes particularly important inside microgrids, where the utility grid may disappear during an outage and local resources must keep the electrical system operating on their own.

What does an inverter do?

Many distributed energy resources naturally produce or store direct-current electricity.

Solar photovoltaic panels produce DC electricity. Batteries store energy in DC form.

Most conventional buildings and utility distribution systems operate primarily with alternating current.

An inverter is the power-electronic interface that converts and controls electricity so those resources can interact with the AC system.

Modern inverters do considerably more than simple DC-to-AC conversion. Their control software determines how they respond to voltage, frequency, power commands and disturbances.

That is where the distinction between grid-following and grid-forming behavior begins.

What is a grid-following inverter?

A grid-following inverter, commonly abbreviated GFL, operates by synchronizing itself with an electrical waveform established by the wider grid or another grid-forming source.

It effectively observes the voltage and frequency of the existing system and injects power according to its control objectives.

This approach has worked well for conventional grid-connected solar because the larger electricity system has historically been dominated by synchronous generators capable of establishing strong voltage and frequency references.

The inverter therefore has something reliable to follow.

The U.S. Department of Energy explains the grid-following concept by noting that conventional inverters depend on signals from the rest of the grid and typically stop supplying power when a major disturbance removes that reference.

What is a grid-forming inverter?

A grid-forming inverter, commonly abbreviated GFM, is controlled so it can establish or regulate the voltage and frequency conditions needed by an inverter-based electrical system.

Instead of merely following an existing waveform, the inverter can behave more like a source around which other electrical resources operate.

DOE’s advanced microgrid control research describes grid-forming inverters as capable of regulating terminal voltage and frequency without requiring an external voltage source.

That capability can allow inverter-based distributed energy resources to contribute to maintaining voltage and frequency in an islanded microgrid.

Grid-forming vs grid-following inverters at a glance

Why grid-following worked for the traditional grid

The conventional electricity system contains large rotating generators.

Those machines provide an established electrical environment that inverter-based resources can synchronize with.

When solar represented a relatively small fraction of total generation, requiring its inverters to follow the surrounding system was logical.

The inverter did not need to create the grid. It only needed to connect safely and deliver power into one that already existed.

But that assumption becomes more complicated as more generation is connected through power electronics.

What changes as inverter-based resources grow?

Imagine an electrical system in which nearly every generator waits for someone else to establish voltage and frequency.

Eventually, the question becomes obvious: what is everyone following?

The National Renewable Energy Laboratory’s grid-forming inverter research roadmap identified this issue as renewable and inverter-based resources take on responsibilities historically provided by conventional generators.

Grid-forming control is one potential part of that transition.

Why grid-forming inverters matter for microgrids

The distinction becomes easier to understand when a microgrid disconnects from the utility.

Before the outage, grid-following solar and battery inverters may have been synchronizing with the larger electrical system.

After islanding, that external reference is gone.

Something inside the microgrid must establish appropriate voltage and frequency conditions.

Historically, a synchronous generator could perform that function.

A grid-forming battery inverter creates another option.

This complements the broader process described in Microgrid Media’s guide to how microgrids keep critical loads powered during grid outages. Islanding is not simply a matter of opening a switch; the local electrical system must remain stable after separation.

Grid-forming does not mean the inverter runs the entire microgrid by itself

The term can create a misleading impression.

A grid-forming inverter does not eliminate the need for microgrid controls, protection systems, energy management or adequate generation.

It performs an important electrical-control function within the larger system.

The microgrid controller may decide which resources should operate, how much power a battery should provide and which loads receive priority.

Grid-forming controls determine how an inverter behaves electrically while executing those operating objectives.

DOE’s April 2026 microgrid control and protection strategy treats grid-forming controls, microgrid controllers and protection coordination as related but distinct technical challenges.

Grid-forming batteries

Battery energy storage is a particularly important application for grid-forming controls.

Batteries are electronically interfaced, respond rapidly and can both absorb and supply power.

With suitable inverter controls and system design, a battery can help establish the electrical reference for an islanded microgrid while other resources operate around it.

The battery still has an energy-duration constraint.

A grid-forming inverter changes how the battery interacts electrically with the system; it does not create unlimited stored energy.

That distinction matters for projects such as the CPS Energy island-capable battery microgrid in San Antonio, where storage and microgrid architecture must ultimately support both normal grid-connected operation and resilience objectives.

What is black start?

Black start is the ability to energize an electrical system after it has gone completely dark without relying on power from the wider grid.

Conventional grid-following inverters generally cannot simply energize a dead system because there is no established waveform for them to follow.

Grid-forming technology can be designed to help establish that initial electrical environment.

DOE notes that grid-forming inverters create opportunities for inverter-based resources to contribute to independent grid restart, although actual black-start capability depends on the inverter, controls, battery or generation source, protection system and overall electrical design.

It is therefore incorrect to assume that every product labeled grid-forming automatically gives an entire facility black-start capability.

Grid-forming inverters and renewable microgrids

The technology becomes particularly interesting as microgrids attempt to operate with very high shares of renewable generation.

A microgrid built around conventional generators already contains rotating machines capable of establishing an electrical reference.

A microgrid attempting to operate primarily with solar and batteries is much more dependent on power electronics.

NREL and San Diego Gas & Electric have demonstrated grid-forming inverter operation at the Borrego Springs Microgrid, including work involving renewable-resource islanding and black start.

That research illustrates why grid-forming technology is closely connected to the development of increasingly inverter-dominated microgrids.

Do all resources in a microgrid need to be grid-forming?

No.

A microgrid can contain a mixture of grid-forming and grid-following resources.

For example, one battery inverter may establish the local electrical reference while several solar inverters follow that reference and deliver power.

A synchronous generator can also operate alongside both types of inverter.

Determining the appropriate combination requires engineering analysis of system size, resource characteristics, protection, load behavior and operating modes.

Recent NREL hardware research has specifically examined microgrids containing different proportions of grid-forming and grid-following inverters alongside diesel generation, showing that different configurations create different stability and transition challenges.

Grid-forming inverters do not eliminate system inertia challenges

Traditional synchronous generators contain rotating mass that naturally contributes physical inertia to the power system.

Inverter-based resources do not provide that same mechanical behavior.

Grid-forming controls can be designed to provide rapid frequency and voltage response, but engineers still need to consider system dynamics, protection and interactions among multiple resources.

DOE’s 2026 strategy identifies low system inertia, lower short-circuit current and uncertainty from distributed generation among the technical challenges facing islanded microgrids with high levels of power-electronic resources.

Protection becomes more complicated

Traditional electrical protection schemes were developed around the fault-current characteristics of conventional rotating generators.

Inverters behave differently during faults.

As a result, increasing inverter penetration can affect how protection devices detect and isolate electrical problems.

DOE specifically identifies coordination between grid-forming controls and protection systems as an area requiring continued development.

This is one reason grid-forming capability should be treated as part of a complete power-system design rather than as a standalone equipment feature.

What about data-center microgrids?

Large data centers are emerging as another important application for sophisticated inverter and microgrid controls.

Battery systems can respond quickly to rapid load changes while on-site generators provide longer-duration energy.

Microgrid Media’s cornerstone analysis of why data centers are turning to microgrids and battery storage explains how AI-driven power requirements are increasing interest in integrated behind-the-meter systems.

One recent example is the 350 MW Ohio AI data-center microgrid with 430 MWh of battery storage, which combines batteries with multiple forms of firm on-site generation.

The precise inverter-control architecture of an individual project should not be assumed unless disclosed, but hybrid projects like these illustrate why coordination among power electronics, generators and microgrid controls is becoming increasingly important.

Are grid-forming inverters better than grid-following inverters?

Not in every application.

Grid-following controls remain appropriate and widely used for many resources connected to strong electrical systems.

Grid-forming capability addresses a different need: supporting electrical systems where inverter-based resources must assume more responsibility for establishing and stabilizing grid conditions.

The correct question is therefore not which technology is universally superior.

It is which electrical behavior the power system needs from each resource.

Frequently Asked Questions

What is the main difference between grid-forming and grid-following inverters?

A grid-following inverter synchronizes with an existing electrical waveform. A grid-forming inverter can establish or regulate voltage and frequency so inverter-based resources can support an electrical system without depending entirely on an outside grid reference.

Can a grid-following inverter operate off-grid?

It can operate inside an off-grid system when another suitable resource establishes the voltage and frequency reference it needs. Grid-following behavior alone does not normally establish the electrical system.

Can a grid-forming inverter start a microgrid after a blackout?

Grid-forming technology can support black-start capability, but the complete system must be designed for black start. The inverter label alone does not guarantee that an entire microgrid can restart from a de-energized condition.

Are battery inverters grid-forming?

Some battery inverters support grid-forming control modes while others are primarily grid-following. Capabilities depend on the equipment, firmware, system design and application.

Do solar inverters use grid-forming controls?

Most conventional grid-connected solar installations have historically used grid-following controls, although grid-forming photovoltaic inverter technology is an active area of development and demonstration.

Why are grid-forming inverters important for renewable microgrids?

Microgrids with high shares of solar and battery resources may have fewer synchronous generators available to establish voltage and frequency. Grid-forming controls allow inverter-based resources to assume more of that responsibility.

The bottom line

The difference between grid-forming and grid-following inverters is fundamentally about the electrical reference each device uses.

Grid-following inverters work extremely well when a strong electrical system already exists for them to follow.

Grid-forming inverters become increasingly important when batteries, solar and other inverter-based resources need to help establish and stabilize that electrical system themselves.

For microgrids, that distinction can become critical the moment the utility grid disappears.

As power systems incorporate more batteries and renewable generation, understanding who follows the grid — and who can help form it — will become an increasingly important part of designing reliable inverter-based energy systems.

Jonas Muthoni

Jonas Muthoni is Editor-in-Chief of Microgrid Media, where he oversees reporting and analysis on microgrids, energy storage, distributed energy resources, data center power demand, grid modernization, resilience, renewable energy, and electricity policy and markets. His work focuses on the infrastructure, technologies, and regulatory developments reshaping the power system.

As Editor-in-Chief, Jonas leads Microgrid Media’s editorial strategy and standards, including story selection, source verification, technical accuracy, and the development of original reporting and analysis. His coverage draws on regulatory filings, government records, utility and company disclosures, technical documentation, and independent industry sources to explain significant developments across the evolving energy system.