You send out a switchgear inquiry and two quotes come back. One says "air-insulated." The other says "GIS." The second is nearly double the price, and nobody explains why.
Most online comparisons answer with "it depends on your project." That is true, but it does not help a buyer who has a tender deadline. In practice, the AIS vs GIS decision for distribution projects comes down to three questions asked in the right order: what voltage class are you buying, how much room do you have, and who will maintain the equipment in ten years?
This guide walks through those questions so you can write a tighter specification and compare quotes fairly.
Step 1: Fix the Voltage Class First
Many AIS vs GIS articles put a 12kV switch room and a 110kV substation in the same table. That is why the numbers you find online contradict each other. One source says GIS costs 1.5 times more, another says three times. One says GIS needs 10% of the floor space, another says 65%.
The gap comes from comparing different voltage levels and different product types.
For most industrial plants, mines, real estate projects and distributors' stock, the relevant range is 12kV and 40.5kV. At this level, the practical choice is usually among three families:
- Withdrawable (handcart-type) air-insulated cabinets
- Fixed-type, metal-enclosed air-insulated cabinets
- Compact gas-insulated units, commonly ring main units
Once you name the voltage class, the comparison becomes much more concrete.
Step 2: The Four Decision Points
1. Floor space: GIS's one clear advantage
Air-insulated switchgear (AIS) relies on air gaps between live parts. Air has lower dielectric strength than a sealed insulating gas, so the cabinet needs more clearance and more room. Gas-insulated switchgear (GIS) seals live parts inside a gas-filled metal enclosure, so the footprint shrinks.
Published reductions range from roughly one-third to well over half, depending on voltage and brand. The saving is real, but it only matters if space is actually expensive. In a city basement, on an offshore platform or in a crowded substation, it matters a lot. In a factory with a spare room, it often does not.
2. Cost: look past the unit price
Quotes commonly put GIS at about 1.5 to 2.5 times the price of comparable AIS per unit, though the multiple varies with voltage class and manufacturer.
Unit price is only part of the story. Total cost includes:
- Building and civil work (GIS saves here)
- Installation and commissioning
- Routine maintenance and spare parts
- Cost of an unplanned outage
A useful rule: if you already have a suitable switch room, AIS almost always wins on total cost. GIS starts to win when land or building cost is high and the space saved is large.
3. Maintenance: easy to see versus sealed
AIS is open to inspection. A trained local electrician can check contacts, clean insulators and replace parts without special tools. The downside is that exposed parts collect dust, moisture and sometimes insects or small animals, so cleaning is part of the routine.
GIS is sealed, so routine upkeep is lighter. But when something goes wrong inside the enclosure, diagnosis and repair usually need specialist staff and equipment. "Low maintenance" is not "no maintenance," and repairs can take longer.
Ask yourself honestly: is there a team near the site that can service a sealed, gas-filled unit? In many regions the answer is no, and that decides the matter.
4. SF6 rules: a buyer's compliance risk
Many GIS designs use SF6 gas, a powerful greenhouse gas. The EU's F-gas Regulation (EU) 2024/573 bans F-gases in new medium-voltage switchgear up to 24kV from 1 January 2026, and extends the ban to 24–52kV equipment from 1 January 2030. Other regions are moving in the same direction.
If your project, or your customer's project, is in or may be exported to a regulated market, this is a compliance question, not just an environmental one. Always ask the supplier to state the insulating and switching medium in writing. Also note that "GIS" and "SF6" are not exactly the same thing: SF6-free gas-insulated designs exist, so check the medium rather than assuming.
Gangheng XGN15-12(F/F.R) Box-Type Fixed AC Metal-Clad Switchgear
When to Choose Which
| Your situation | Likely better fit |
|---|---|
| Spare switch room, standard 12kV or 40.5kV distribution | AIS |
| Limited budget, local maintenance staff | AIS |
| Future expansion expected | AIS (easier to add cabinets) |
| Very tight space, underground or urban site | GIS |
| Heavily polluted, salty or humid site | GIS, or AIS with suitable design |
| Target market restricts SF6 | AIS, or SF6-free gas-insulated |
Neither is better in general. But for typical distribution projects with available space, AIS is usually the more economical and easier-to-support option.
Which Air-Insulated Cabinet for Which Job?
If AIS fits your project, the next choice is the cabinet type. Gangheng Electric, which has been building power distribution equipment since 2004, supplies three common formats.
Withdrawable cabinets for higher voltage duty. For 40.5kV systems, handcart-type HV switchgear lets you pull the breaker out for service without dismantling the cabinet. See our 【HV Switchgear】 GBC-40.5 handcart-type cabinet for this class. Gangheng also delivered a KYN61-40.5 withdrawable switchgear project in Tanzania, where the equipment went from unboxing to energized in five days. Fast on-site installation matters when your crew is working far from the factory.
Fixed cabinets for indoor 12kV rooms. Where you want a simple, robust layout and a lower price, 【Indoor HV Switchgear】 such as the GG1A-12(F) fixed error-prevention cabinet is a common choice. The "error-prevention" design uses mechanical interlocks to stop wrong operation sequences, which protects operators.
Box-type fixed cabinets for compact distribution points. The 【Metal Enclosed Switchgear】 XGN15-12(F/F.R) is a box-type, fixed, indoor cabinet. In the model code, "F" means it is fitted with a load switch, and "F.R" means a load switch–fuse combination unit. It suits ring-main and branch-circuit duty where full breaker-type cabinets would be more than the job needs.
As a rule of thumb: withdrawable for service flexibility and higher voltage, fixed for cost and simplicity, and box-type metal enclosed switchgear for compact secondary distribution.
Product range in real photos: A slideshow of Gangheng's switchgear, transformers and other power distribution products, shot at the factory. For the cabinet types discussed above, you can request detailed drawings and photos from our team before placing an order.
Buyer's Checklist: Avoid These Mistakes
Before you compare quotes, put these items into your specification:
- Voltage class and short-circuit rating. Without them, quotes are not comparable.
- Insulating and switching medium. Require it in writing, including whether any F-gas is used.
- Standards. Gangheng's products follow Chinese national standards (GB), and can be built to other standards such as ANSI/IEEE or BS on request. State yours up front.
- Site altitude and environment. Tell the supplier early so the factory can assess the design.
- Expansion plans. Say whether you may add cabinets later.
- Customization. If you need non-standard dimensions or layouts, supply the transformer size and drawings. If you do not have them, supply the site conditions, equipment power and required functions, and the factory will propose a design. Gangheng's price is the same for standard and non-standard designs, though a non-standard cabinet may come out wider.
Bending a cabinet panel at Gangheng's factory. Non-standard sizes are built to customer drawings.
7. Lead time and quantity. There is no minimum order, and even one unit can be shipped. Delivery depends on order size, typically between about 30 and 60 days.
8. Warranty. Gangheng offers a 12-month warranty after acceptance, with coverage for hidden defects for five years afterward.
Conclusion: What to Do Next
The AIS vs GIS question is easier than it looks once you stop treating it as a technology contest.
- Fix your voltage class first, so you compare like with like.
- If you have space, a local maintenance team and no SF6 restriction, AIS is usually the better-value choice.
- If space is scarce or the site is harsh, price GIS seriously, and confirm the gas type and your target market's rules.
- Put the insulating medium, standards and site conditions in your RFQ so every supplier quotes the same thing.
If you are unsure which cabinet type fits your project, send your single-line diagram and site details to Gangheng's engineers, who can recommend a configuration before you request formal quotes.
FAQ
What is the main difference between AIS and GIS switchgear?
AIS uses ambient air to insulate live parts, while GIS seals them inside a metal enclosure filled with insulating gas. That is why GIS is more compact and AIS is easier to inspect.
Which is better, AIS or GIS?
Neither is better in every case. AIS suits projects with available space and local maintenance capability, while GIS suits tight, urban or harsh-environment sites.
Why is GIS more expensive?
Sealed enclosures, gas handling and tighter manufacturing control add cost. The premium is often partly offset by smaller buildings and less civil work.
Is GIS maintenance-free?
No. Routine upkeep is lighter, but internal faults need specialist diagnosis and repair, and gas systems need monitoring.
Does SF6 regulation affect my order?
It can, especially for projects in or exported to the EU. Ask your supplier to state the insulating medium in writing, and check current rules for your market.