---
title: "Gas-insulated vs. air-insulated switchgear | Entogo"
description: "Gas-insulated switchgear seals live parts in gas for a compact, low-maintenance lineup; air-insulated switchgear stays larger but fully serviceable and…"
url: https://entogo.ca/insights/gas-insulated-vs-air-insulated-switchgear/
lang: en
type: article
image: https://entogo.ca/_astro/gas-insulated-vs-air-insulated-switchgear.DBsOTNus.jpg
datePublished: 2026-08-01
dateModified: 2026-08-01
site: https://entogo.ca/
llms: https://entogo.ca/llms.txt
---

Home › Insights › Gas-insulated vs. air-insulated switchgear: how to choose

Power & Distribution

# Gas-insulated vs. air-insulated switchgear: how to choose

Entogo August 1, 2026

![Medium-voltage switchgear lineup in an electrical substation and power distribution room](https://entogo.ca/_astro/gas-insulated-vs-air-insulated-switchgear.DBsOTNus_1TePXd.webp)

Photo — Novoklimov · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:High_voltage_switchgear.jpg) · [CC0](http://creativecommons.org/publicdomain/zero/1.0/deed.en)

In short

Gas-insulated switchgear seals live parts in gas for a compact, low-maintenance lineup; air-insulated switchgear stays larger but fully serviceable and gas-free. The right choice turns on footprint, environment, voltage class, and tightening SF6 rules.

## Should a project specify gas-insulated or air-insulated switchgear?

Medium-voltage distribution has two established ways to keep energized parts from flashing over: separate them with air, or seal them inside an enclosure filled with an insulating gas. **Air-insulated switchgear (AIS)** relies on clearance and solid barriers in ambient air. **Gas-insulated switchgear (GIS)** shrinks those clearances by surrounding the conductors and switching devices with a dielectric gas inside a sealed metal enclosure. Both switch, isolate, and protect the same circuits; they differ in size, maintenance, environmental exposure, and — increasingly — in how regulators treat the gas itself.

The choice is rarely about performance alone. It is a site decision that weighs available floor area, ambient conditions, voltage class, service philosophy, and a shifting compliance picture around **SF6**. Getting it wrong means either paying for a building larger than it needs to be, or installing sealed equipment that a jurisdiction is about to restrict.

## How the two technologies differ

### The insulating medium sets everything else

In AIS, dielectric strength comes from air gaps, so bus bars, breakers, and terminations need physical separation and are typically reachable for inspection. That makes the lineup larger but keeps live parts visible and serviceable. GIS replaces most of those air gaps with pressurized gas inside a grounded shell, letting conductors sit far closer together.

The practical trade-off shows up in maintenance. As one manufacturer’s application guidance notes, in GIS “primary circuits and components are contained within a sealed tank or covered with solid encapsulated insulation,” so they “are not subject to destructive effects of the surrounding environment, thus requiring minimal or no maintenance for long periods.” AIS, by contrast, can see its “performance and dielectric integrity … negatively affected by environmental contaminants and humidity,” so “more elaborate and frequent maintenance may be required.” Sealing is an advantage in harsh or dirty environments and a limitation where crews expect to open and inspect primary compartments directly. Both approaches are available as [metal-clad switchgear](https://entogo.ca/products/metal-clad-switchgear/) with compartmentalized, drawout breakers, or as simpler [metal-enclosed switchgear](https://entogo.ca/products/metal-enclosed-switchgear/) for fixed-mounted devices.

### Footprint and where it matters

Space is where GIS earns its premium — but only above a voltage threshold. According to the same engineering guidance, “at 5 and 15 kV, lineups of metal-clad switchgear and GIS have similar footprints,” while “at 27 and 38 kV, GIS offers a much smaller footprint” and “can reduce the footprint by up to 60 per cent, saving building costs and freeing up space for other use.” At 15 kV and below, the compactness case for [gas-insulated switchgear](https://entogo.ca/products/gas-insulated-switchgear/) is weak; the argument strengthens sharply at 27 kV and 38 kV, and in dense urban rooms, rooftop electrical spaces, and retrofit vaults where every square metre is expensive.

## What SF6 rules are changing

The gas most GIS has historically used is **sulfur hexafluoride (SF6)** — an excellent insulator and arc-quenching medium, and a potent greenhouse gas. The U.S. EPA classifies SF6 among “high-GWP gases” whose global warming potentials “can be in the thousands or tens of thousands,” and which “persist in the atmosphere for hundreds or thousands of years.”

That profile is driving a wave of state action. California’s Air Resources Board finalized amendments in 2022 to “phase out use of SF6 in gas-insulated equipment (GIE) starting in 2025.” New York “implements a voltage-based phaseout of SF6-gas insulated equipment (GIE) beginning in 2027.” Massachusetts caps GIS at “a maximum annual SF6 leak rate of 1 percent for GIS purchases after 2015.” The direction is one-way: SF6-filled equipment now carries inventory, leak-tracking, and end-of-life obligations, and in some states a shrinking window to buy it at all. SF6-free GIS — using vacuum interruption with alternative gases or dry air — is maturing to fill the gap, and any GIS specification written today should state which insulating medium the design uses and how the owner will meet local reporting rules.

## Where each approach makes sense

GIS fits space-constrained, higher-MV sites: substations feeding [data centers](https://entogo.ca/solutions/data-centers/), urban distribution, indoor rooms at 27–38 kV, and coastal or industrial environments where sealed primary parts resist contamination. AIS fits sites with room to build, lower voltage classes, owners who value direct access to primary compartments, and projects where SF6 policy or corporate sustainability targets discourage gas-filled equipment. Many campuses mix both — AIS at 5–15 kV lineups and GIS where footprint drives the design — often alongside [low-voltage switchgear and MCCs](https://entogo.ca/products/low-voltage-switchgear-mcc/) downstream.

## What a buyer should specify

Start with the governing standards as context. Medium-voltage switchgear is specified against the **IEC 62271** series and the **IEEE C37.20** family, with gas-insulated substations above 52 kV governed by **IEEE C37.122** and **IEC 62271-203**; installation follows the **NEC** and Canadian **CEC**. From there, pin down rated voltage and short-circuit withstand; arc-resistance class if required; the insulating medium (SF6 or SF6-free) and the leak-rate and reporting obligations that come with it; the maintenance model the crews can actually support; and the true available floor area, since that is what decides whether the GIS premium pays back.

Entogo designs and builds both AIS and GIS lineups — from metal-clad and gas-insulated switchgear to [pad-mounted RMUs](https://entogo.ca/products/pad-mounted-switchgear-rmu/) and packaged units for [substations and power distribution](https://entogo.ca/solutions/substations-power-distribution/) and [utility](https://entogo.ca/solutions/utilities/) projects — designed and built to the applicable IEEE and IEC standards; UL (cULus)/CSA certifiable on request. Because the switchgear, transformers, and enclosures come from one vertically integrated factory, a lineup can be matched to a site’s footprint, voltage class, and gas policy without the multi-year waits that dominate today’s market.

- switchgear
- gas-insulated switchgear
- power distribution
- substations
- SF6

Glossary: [Gas-insulated switchgear](https://entogo.ca/glossary/#gas-insulated-switchgear) [Voltage class](https://entogo.ca/glossary/#voltage-class) [Metal-clad switchgear](https://entogo.ca/glossary/#metal-clad-switchgear) [Metal-enclosed](https://entogo.ca/glossary/#metal-enclosed-switchgear) [Low-voltage switchgear](https://entogo.ca/glossary/#low-voltage-switchgear-ul-1558)

FAQ

## Common questions

- **What is the difference between GIS and AIS switchgear**: GIS seals live parts inside a sealed enclosure filled with an insulating gas, so it is compact and needs little maintenance. AIS uses air as the insulator, so it is larger but fully serviceable and gas-free.
- **Is gas-insulated switchgear always smaller than air-insulated**: No. At 5 and 15 kV the footprints are similar. The space savings grow at 27 and 38 kV, where GIS can cut the footprint by up to 60 percent.
- **Does gas-insulated switchgear use SF6**: Traditionally yes, though SF6 is a potent greenhouse gas now facing state phase-outs. SF6-free designs using vacuum interruption or alternative gases are increasingly specified.
- **When should I choose air-insulated switchgear**: Pick AIS when floor space is available, when crews want to inspect and service primary parts directly, or when SF6 rules or owner policy rule out gas-filled equipment.
- **What standards govern gas-insulated switchgear**: Medium-voltage switchgear is built to the IEC 62271 series and the IEEE C37.20 family, while gas-insulated substations above 52 kV follow IEEE C37.122 and IEC 62271-203.

Keep reading

## Related insights

[![Distribution transformer and secondary conductors feeding low-voltage distribution equipment, governed by NEC 240.21(C) tap rules and CEC Rule 26-256](https://entogo.ca/_astro/transformer-secondary-conductors-nec-240-21c-tap-rules.BX_tOclr_UXL9N.webp) Power & Distribution ### How long can transformer secondary conductors be? NEC 240.21(C) tap rules and CEC 26-256 Transformer secondary conductors get no next-size-up rule. NEC 240.21(C) allows 10 ft and 25 ft runs with ampacity floors of one-tenth and one-third of the primary device times the voltage ratio; CEC 26-256 instead demands 125% of rated secondary current at any length. View](https://entogo.ca/insights/transformer-secondary-conductors-nec-240-21c-tap-rules/)[![Three-phase distribution transformer and low-voltage switchgear at a North American facility substation](https://entogo.ca/_astro/choosing-a-facility-distribution-voltage.B10infhs_Z2obSGL.webp) Power & Distribution ### 208, 480, or 600 volts? Choosing a facility distribution voltage North American facilities are served at 120/208, 277/480, or 347/600 volts. A higher voltage moves the same power at lower current, cutting conductor size and losses while adding transformer and safety cost. Here is how to match the voltage to the load. View](https://entogo.ca/insights/choosing-a-facility-distribution-voltage/)[![Power transformer at an electrical substation with an on-load tap changer for voltage regulation](https://entogo.ca/_astro/transformer-voltage-regulation-tap-changers.LSKEj7V-_xljGw.webp) Power & Distribution ### De-energized taps or a load tap changer? Specifying transformer voltage regulation A transformer needs voltage regulation when source voltage swings beyond about 5 percent or loads are voltage-sensitive. Fixed de-energized taps correct a standing offset; on-load tap changers hold output steady continuously. Here is how to choose and specify. View](https://entogo.ca/insights/transformer-voltage-regulation-tap-changers/)

Project inquiry

## Turn the brief into a specified system.

[Talk to engineering](https://entogo.ca/contact/)

## Structured data (JSON-LD)

```json
{"@context":"https://schema.org","@type":"Article","headline":"Gas-insulated vs. air-insulated switchgear: how to choose","description":"Gas-insulated switchgear seals live parts in gas for a compact, low-maintenance lineup; air-insulated switchgear stays larger but fully serviceable and gas-free. The right choice turns on footprint, environment, voltage class, and tightening SF6 rules.","image":"https://entogo.ca/_astro/gas-insulated-vs-air-insulated-switchgear.DBsOTNus.jpg","author":{"@id":"https://entogo.ca/#organization"},"publisher":{"@id":"https://entogo.ca/#organization"},"mainEntityOfPage":"https://entogo.ca/insights/gas-insulated-vs-air-insulated-switchgear/","inLanguage":"en","datePublished":"2026-08-01T00:00:00.000Z","dateModified":"2026-08-01T00:00:00.000Z","keywords":"switchgear, gas-insulated switchgear, power distribution, substations, SF6","about":[{"@id":"https://entogo.ca/glossary/#gas-insulated-switchgear"},{"@id":"https://entogo.ca/glossary/#voltage-class"},{"@id":"https://entogo.ca/glossary/#metal-clad-switchgear"},{"@id":"https://entogo.ca/glossary/#metal-enclosed-switchgear"},{"@id":"https://entogo.ca/glossary/#low-voltage-switchgear-ul-1558"}]}
```

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://entogo.ca/"},{"@type":"ListItem","position":2,"name":"Insights","item":"https://entogo.ca/insights/"},{"@type":"ListItem","position":3,"name":"Gas-insulated vs. air-insulated switchgear: how to choose"}]}
```

```json
{"@context":"https://schema.org","@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is the difference between GIS and AIS switchgear","acceptedAnswer":{"@type":"Answer","text":"GIS seals live parts inside a sealed enclosure filled with an insulating gas, so it is compact and needs little maintenance. AIS uses air as the insulator, so it is larger but fully serviceable and gas-free."}},{"@type":"Question","name":"Is gas-insulated switchgear always smaller than air-insulated","acceptedAnswer":{"@type":"Answer","text":"No. At 5 and 15 kV the footprints are similar. The space savings grow at 27 and 38 kV, where GIS can cut the footprint by up to 60 percent."}},{"@type":"Question","name":"Does gas-insulated switchgear use SF6","acceptedAnswer":{"@type":"Answer","text":"Traditionally yes, though SF6 is a potent greenhouse gas now facing state phase-outs. SF6-free designs using vacuum interruption or alternative gases are increasingly specified."}},{"@type":"Question","name":"When should I choose air-insulated switchgear","acceptedAnswer":{"@type":"Answer","text":"Pick AIS when floor space is available, when crews want to inspect and service primary parts directly, or when SF6 rules or owner policy rule out gas-filled equipment."}},{"@type":"Question","name":"What standards govern gas-insulated switchgear","acceptedAnswer":{"@type":"Answer","text":"Medium-voltage switchgear is built to the IEC 62271 series and the IEEE C37.20 family, while gas-insulated substations above 52 kV follow IEEE C37.122 and IEC 62271-203."}}]}
```

_Markdown twin of https://entogo.ca/insights/gas-insulated-vs-air-insulated-switchgear/ — generated at build time from the same content as the HTML page. Company facts, catalogue index and contact: https://entogo.ca/llms.txt_