Oct 28, 2025
GIS vs. AIS: Which Substation Tech Fits Your Project?
Substations need to be insulated for safety reasons. Most modern projects are either gas-insulated substations (GIS) or air-insulated substations (AIS). Both types of technology have their advantages and disadvantages. Engineers need to accommodate everything from environmental conditions to maintenance needs and budgets. They also need to consider space constraints.
When space is at a premium, especially on projects in densely populated urban areas, GIS makes a lot of sense. But there are drawbacks. It goes without saying that every option needs to be considered when developing a new project. Below are some of the more perplexing considerations.
1. Design and Footprint
GIS technology is noted for its compact design. It relies on SF₆ gas for insulation, thereby reducing the project's total footprint. A GIS project can be up to 35% smaller than a comparable AIS project. The technology is well suited to urban and industrial areas where space is hard to come by. It is also an excellent choice for underground substations.
As its name suggests, AIS technology uses air for insulation. Project designs call for larger spaces between components to allow proper air circulation. AIS projects are better suited for rural and suburban locations where there is plenty of land to build on.
2. Environmental Resilience
Every substation needs to resist adverse environmental conditions to some degree. Here again, GIS technology has several advantages that are hard to overlook. A GIS substation is more environmentally resilient because of its sealed design. In coastal and desert regions, it performs better. The same goes for regions experiencing high humidity.
AIS substations perform better where the weather isn't extreme. Moderate climates with lower pollution levels are ideal. Unfortunately, AIS systems are more vulnerable to adverse conditions. They require more maintenance as a result.
3. Maintenance and Reliability
Speaking of maintenance, a well-designed GIS substation can operate virtually maintenance-free. This goes back to its sealed design and SF₆ gas insulation. GIS systems are safer, are subject to fewer outages, and do not present nearly the same level of hazards.
On the other hand, AIS systems require regular inspection and maintenance just to keep up with normal wear and tear. Contamination and weather damage need to be taken care of right away. But because of their exposed nature, they are also at risk of serious damage during severe weather events.
4. Cost and Construction Concerns
So far it seems like GIS systems win the day. With all its advantages, why even consider AIS? For many projects, it boils down to cost. Where space constraints are not an issue, AIS construction is more budget-friendly. AIS systems are simpler to design and easier to build.
A GIS design might be more cost-effective in the long term due to lower maintenance needs. But design and construction costs will be significantly higher. Can the budget support higher upfront costs?
5. Safety and Environmental Concerns
AIS substations win the day on upfront cost. They are also better in terms of environmental impact. The safety aspects are about the same.
From an environmental standpoint, AIS technology is fairly innocuous. But GIS technology is subject is significant global warming potential thanks to its gas. From a safety perspective, AIS could be considered less safe because of higher risks linked to maintenance. But any such risks are negligible in real-world applications.
When space constraints are a concern and the budget can support it, GIS technology is often the better choice for a new substation. But AIS projects continue to be built because they are budget-friendly. They represent reliable technology that we have come to depend on.
Back to All Insights